public void setValueCallback(@Nullable LottieValueCallback<A> valueCallback) {
    if (this.valueCallback != null) {
      this.valueCallback.setAnimation(null);
    }
    this.valueCallback = valueCallback;
    if (valueCallback != null) {
      valueCallback.setAnimation(this);
    }
  }
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