The version of the Gem I had installed was 0.4.0, and since the for_handle filter was implemented in a later version, I wasn’t able to use it. https://rubygems.org/gems/google-apis-youtube_v3/versions/0.4.0
Updating the Gem to a newer version resolved the issue. https://rubygems.org/gems/google-apis-youtube_v3/versions/0.56.0
Thank you to SpicyCatGames for the comment!