:calls: `PATCH /repos/:owner/:repo/milestones/:number <http://developer.github.com/v3/issues/milestones>`_
        :param title: string
        :param state: string
        :param description: string
        :param due_on: date
        :rtype: None

def edit(self, title, state=github.GithubObject.NotSet, description=github.GithubObject.NotSet, due_on=github.GithubObject.NotSet):
        """
        :calls: `PATCH /repos/:owner/:repo/milestones/:number <http://developer.github.com/v3/issues/milestones>`_
        :param title: string
        :param state: string
        :param description: string
        :param due_on: date
        :rtype: None
        """
        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.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:
            post_parameters["due_on"] = due_on.strftime("%Y-%m-%d")
        headers, data = self._requester.requestJsonAndCheck(
            "PATCH",
            self.url,
            input=post_parameters
        )
        self._useAttributes(data)