float getLinearCurrentKeyframeProgress() {
    if (isDiscrete) {
      return 0f;
    }

    Keyframe<K> keyframe = getCurrentKeyframe();
    if (keyframe.isStatic()) {
      return 0f;
    }
    float progressIntoFrame = progress - keyframe.getStartProgress();
    float keyframeProgress = keyframe.getEndProgress() - keyframe.getStartProgress();
    return progressIntoFrame / keyframeProgress;
  }
Returns the progress into the current keyframe between 0 and 1. This does not take into account
any interpolation that the keyframe may have.
lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java