@SuppressLint("Range")
  @FloatRange(from = 0f, to = 1f)
  private float getStartDelayProgress() {
    if (cachedStartDelayProgress == -1f) {
      cachedStartDelayProgress = keyframesWrapper.getStartDelayProgress();
    }
    return cachedStartDelayProgress;
  }
Takes the value of {@link #getLinearCurrentKeyframeProgress()} and interpolates it with
the current keyframe's interpolator.
lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java