':calls: `PUT /user/subscriptions/:owner/:repo <http://developer.github.com/v3/activity/watching>`_
:param subscription: :class:`github.Repository.Repository`
:rtype: None'

def add_to_subscriptions(self, subscription):

    assert isinstance(subscription, github.Repository.Repository), subscription
    (headers, data) = self._requester.requestJsonAndCheck('PUT', ('/user/subscriptions/' + subscription._identity))
