Is this what you are referring to that has docs for send, close and throw in coroutine objects ? 
Coroutine object docs : https://docs.python.org/3/reference/datamodel.html#coroutine-objects

If the above is the one then I think we can improve on the visibility by linking it from other pages since it doesn't show up with Google for 'coroutine close'. I had to use Docs folder in source code and sphinx search in docs.python.org with 'coroutine close' to get there.

Thanks