The documentation for 3.5 was deliberated removed from the pull down lists of current docsets as 3.5 is now in security-fix-only mode; the 3.5 documentation is only updated when a new security release is made and general doc changes to it are no longer made.  You can find a link to the docsets for 3.5.x and all Python releases on the Python Documentation By Version page (https://www.python.org/doc/versions/) which is linked to from a number of places, including the index page of the current and past Python versions docsets (e.g. https://docs.python.org/3/) and from the main python.org doc page (https://www.python.org/doc/).