/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License
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*/
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package com.android.systemui.classifier;
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import android.os.Build;
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import android.os.SystemProperties;
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import android.view.MotionEvent;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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/**
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* A classifier which calculates the variance of differences between successive angles in a stroke.
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* For each stroke it keeps its last three points. If some successive points are the same, it
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* ignores the repetitions. If a new point is added, the classifier calculates the angle between
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* the last three points. After that, it calculates the difference between this angle and the
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* previously calculated angle. Then it calculates the variance of the differences from a stroke.
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* To the differences there is artificially added value 0.0 and the difference between the first
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* angle and PI (angles are in radians). It helps with strokes which have few points and punishes
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* more strokes which are not smooth.
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*
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* This classifier also tries to split the stroke into two parts in the place in which the biggest
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* angle is. It calculates the angle variance of the two parts and sums them up. The reason the
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* classifier is doing this, is because some human swipes at the beginning go for a moment in one
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* direction and then they rapidly change direction for the rest of the stroke (like a tick). The
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* final result is the minimum of angle variance of the whole stroke and the sum of angle variances
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* of the two parts split up. The classifier tries the tick option only if the first part is
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* shorter than the second part.
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*
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* Additionally, the classifier classifies the angles as left angles (those angles which value is
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* in [0.0, PI - ANGLE_DEVIATION) interval), straight angles
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* ([PI - ANGLE_DEVIATION, PI + ANGLE_DEVIATION] interval) and right angles
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* ((PI + ANGLE_DEVIATION, 2 * PI) interval) and then calculates the percentage of angles which are
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* in the same direction (straight angles can be left angels or right angles)
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*/
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public class AnglesClassifier extends StrokeClassifier {
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private HashMap<Stroke, Data> mStrokeMap = new HashMap<>();
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public static final boolean VERBOSE = SystemProperties.getBoolean("debug.falsing_log.ang",
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Build.IS_DEBUGGABLE);
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private static String TAG = "ANG";
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public AnglesClassifier(ClassifierData classifierData) {
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mClassifierData = classifierData;
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}
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@Override
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public String getTag() {
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return TAG;
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}
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@Override
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public void onTouchEvent(MotionEvent event) {
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int action = event.getActionMasked();
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if (action == MotionEvent.ACTION_DOWN) {
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mStrokeMap.clear();
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}
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for (int i = 0; i < event.getPointerCount(); i++) {
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Stroke stroke = mClassifierData.getStroke(event.getPointerId(i));
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if (mStrokeMap.get(stroke) == null) {
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mStrokeMap.put(stroke, new Data());
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}
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mStrokeMap.get(stroke).addPoint(stroke.getPoints().get(stroke.getPoints().size() - 1));
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}
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}
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@Override
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public float getFalseTouchEvaluation(int type, Stroke stroke) {
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Data data = mStrokeMap.get(stroke);
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return AnglesVarianceEvaluator.evaluate(data.getAnglesVariance(), type)
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+ AnglesPercentageEvaluator.evaluate(data.getAnglesPercentage(), type);
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}
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private static class Data {
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private final float ANGLE_DEVIATION = (float) Math.PI / 20.0f;
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private List<Point> mLastThreePoints = new ArrayList<>();
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private float mFirstAngleVariance;
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private float mPreviousAngle;
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private float mBiggestAngle;
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private float mSumSquares;
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private float mSecondSumSquares;
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private float mSum;
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private float mSecondSum;
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private float mCount;
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private float mSecondCount;
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private float mFirstLength;
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private float mLength;
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private float mAnglesCount;
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private float mLeftAngles;
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private float mRightAngles;
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private float mStraightAngles;
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public Data() {
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mFirstAngleVariance = 0.0f;
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mPreviousAngle = (float) Math.PI;
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mBiggestAngle = 0.0f;
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mSumSquares = mSecondSumSquares = 0.0f;
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mSum = mSecondSum = 0.0f;
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mCount = mSecondCount = 1.0f;
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mLength = mFirstLength = 0.0f;
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mAnglesCount = mLeftAngles = mRightAngles = mStraightAngles = 0.0f;
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}
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public void addPoint(Point point) {
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// Checking if the added point is different than the previously added point
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// Repetitions are being ignored so that proper angles are calculated.
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if (mLastThreePoints.isEmpty()
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|| !mLastThreePoints.get(mLastThreePoints.size() - 1).equals(point)) {
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if (!mLastThreePoints.isEmpty()) {
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mLength += mLastThreePoints.get(mLastThreePoints.size() - 1).dist(point);
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}
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mLastThreePoints.add(point);
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if (mLastThreePoints.size() == 4) {
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mLastThreePoints.remove(0);
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float angle = mLastThreePoints.get(1).getAngle(mLastThreePoints.get(0),
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mLastThreePoints.get(2));
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mAnglesCount++;
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if (angle < Math.PI - ANGLE_DEVIATION) {
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mLeftAngles++;
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} else if (angle <= Math.PI + ANGLE_DEVIATION) {
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mStraightAngles++;
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} else {
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mRightAngles++;
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}
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float difference = angle - mPreviousAngle;
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// If this is the biggest angle of the stroke so then we save the value of
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// the angle variance so far and start to count the values for the angle
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// variance of the second part.
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if (mBiggestAngle < angle) {
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mBiggestAngle = angle;
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mFirstLength = mLength;
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mFirstAngleVariance = getAnglesVariance(mSumSquares, mSum, mCount);
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mSecondSumSquares = 0.0f;
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mSecondSum = 0.0f;
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mSecondCount = 1.0f;
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} else {
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mSecondSum += difference;
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mSecondSumSquares += difference * difference;
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mSecondCount += 1.0;
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}
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mSum += difference;
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mSumSquares += difference * difference;
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mCount += 1.0;
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mPreviousAngle = angle;
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}
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}
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}
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public float getAnglesVariance(float sumSquares, float sum, float count) {
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return sumSquares / count - (sum / count) * (sum / count);
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}
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public float getAnglesVariance() {
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float anglesVariance = getAnglesVariance(mSumSquares, mSum, mCount);
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if (VERBOSE) {
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FalsingLog.i(TAG, "getAnglesVariance: (first pass) " + anglesVariance);
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FalsingLog.i(TAG, " - mFirstLength=" + mFirstLength);
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FalsingLog.i(TAG, " - mLength=" + mLength);
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}
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if (mFirstLength < mLength / 2f) {
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anglesVariance = Math.min(anglesVariance, mFirstAngleVariance
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+ getAnglesVariance(mSecondSumSquares, mSecondSum, mSecondCount));
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if (VERBOSE) FalsingLog.i(TAG, "getAnglesVariance: (second pass) " + anglesVariance);
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}
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return anglesVariance;
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}
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public float getAnglesPercentage() {
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if (mAnglesCount == 0.0f) {
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if (VERBOSE) FalsingLog.i(TAG, "getAnglesPercentage: count==0, result=1");
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return 1.0f;
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}
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final float result = (Math.max(mLeftAngles, mRightAngles) + mStraightAngles) / mAnglesCount;
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if (VERBOSE) {
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FalsingLog.i(TAG, "getAnglesPercentage: left=" + mLeftAngles + " right="
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+ mRightAngles + " straight=" + mStraightAngles + " count=" + mAnglesCount
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+ " result=" + result);
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}
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return result;
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}
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}
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}
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