NameError: uninitialized constant YouTubeIt::OAuth2Client

[kashifghaffarasim]

I got above error
client = YouTubeIt::OAuth2Client.new(client_access_token: get_access_token["access_token"], client_refresh_token: key, client_id: "1026874697644-4dq6e9qhimuqb9j3j7gbabj7oh22.com", client_secret: "key", dev_key: "key")

Any idea in rails 5.1.4.