is
Returns whether the audio and video resource for the given video fill or audio block is loaded. Note that the function is unstable and mared with UnstableEngineApi. A buffer:// source counts as loaded once the engine has read its file, with the images that a Lottie references. A missing or empty buffer, or raw audio samples on an audio block, count as loaded.
Return
whether the resource is loaded.
Parameters
block
the video fill or audio block.