def add_to_watched(self, watched):
assert isinstance(watched, github.Repository.Repository), watched<EOL>headers, data = self._requester.requestJsonAndCheck(<EOL>"<STR_LIT>",<EOL>"<STR_LIT>" + watched._identity + "<STR_LIT>",<EOL>input={"<STR_LIT>": True}<EOL>)<EOL>
:calls: `PUT /repos/:owner/:repo/subscription <http://developer.github.com/v3/activity/watching>`_
:param watched: :class:`github.Repository.Repository`
:rtype: None