code: def milestone(self, number):
          
          json = None
          if int(number) > 0:
              url = self._build_url('milestones', str(number),
                                    base_url=self._api)
              json = self._json(self._get(url), 200)
          return Milestone(json, self) if json else None
docs: Get the milestone indicated by ``number``.
  
          :param int number: (required), unique id number of the milestone
          :returns: :class:`Milestone <github3.issues.milestone.Milestone>`