'Get the specified deploy key.
:param int id_num: (required), id of the key
:returns: :class:`~github3.users.Key` if successful, else None'

@requires_auth
def key(self, id_num):

    json = None
    if (int(id_num) > 0):
        url = self._build_url(u'keys', str(id_num), base_url=self._api)
        json = self._json(self._get(url), 200)
    return (users.Key(json, self) if json else None)
