def mark_notifications_as_read(self, last_read_at=datetime.datetime.utcnow()):
assert isinstance(last_read_at, datetime.datetime)<EOL>put_parameters = {<EOL>"<STR_LIT>": last_read_at.strftime('<STR_LIT>')<EOL>}<EOL>headers, data = self._requester.requestJsonAndCheck(<EOL>"<STR_LIT>",<EOL>self.url + "<STR_LIT>",<EOL>input=put_parameters<EOL>)<EOL>
:calls: `PUT /repos/:owner/:repo/notifications <https://developer.github.com/v3/activity/notifications>`_
:param last_read_at: datetime