As explained in the project proposal, the idea to retrieve all video ids is to start from a starting set of channels, then list their videos using YouTube Data API v3 PlaylistItems: list, then list the comments on their videos and then restart the process as we potentially retrieved new channels thanks to comment authors on videos from already known channels.

For a given channel, there is a single way to list comments users published on it:
As explained, YouTube Data API v3 PlaylistItems: list endpoint enables us to list the channel videos up to 20,000 videos and CommentThreads: list and Comments: list endpoints enable us to retrieve their comments

We can multi-thread this process by channel or we can multi-thread per videos of a given channel.
As would like to proceed channel per channel, the question is **how much time does it take to retrieve all comments from the biggest YouTube channel? If the answer is a long period of time, then multi-threading per videos of a given channel may make sense.**

**In fact should proceed fastly with CommentThreads: list with `allThreads...` when possible**
**do I have an example of channels where commentthreads: list work but doesn't list a comment of a video ... ?**

Have to proceed with a breadth-first search approach as treating all *child* channels might take a time equivalent to treating the whole original tree.