code: def create_milestone(self, title, state=github.GithubObject.NotSet, description=github.GithubObject.NotSet, due_on=github.GithubObject.NotSet):
          
          assert isinstance(title, (str, unicode)), title
          assert state is github.GithubObject.NotSet or isinstance(state, (str, unicode)), state
          assert description is github.GithubObject.NotSet or isinstance(description, (str, unicode)), description
          assert due_on is github.GithubObject.NotSet or isinstance(due_on, (datetime.datetime, datetime.date)), due_on
          post_parameters = {
              "title": title,
          }
          if state is not github.GithubObject.NotSet:
              post_parameters["state"] = state
          if description is not github.GithubObject.NotSet:
              post_parameters["description"] = description
          if due_on is not github.GithubObject.NotSet:
              if isinstance(due_on, datetime.date):
                  post_parameters["due_on"] = due_on.strftime("%Y-%m-%dT%H:%M:%SZ")
              else:
                  post_parameters["due_on"] = due_on.isoformat()
          headers, data = self._requester.requestJsonAndCheck(
              "POST",
              self.url + "/milestones",
              input=post_parameters
          )
          return github.Milestone.Milestone(self._requester, headers, data, completed=True)
docs: :calls: `POST /repos/:owner/:repo/milestones <http://developer.github.com/v3/issues/milestones>`_
          :param title: string
          :param state: string
          :param description: string
          :param due_on: datetime
          :rtype: :class:`github.Milestone.Milestone`