<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def update(self, id, label=None, status=None, master=None):
 """ Update an Identity :param label: The label to give this new identity :param status: The status of this identity. Default: 'active' :param master: Represents whether this identity is a master. Default: False :return: dict of REST API output with headers attached :rtype: :class:`~datasift.request.DictResponse` :raises: :class:`~datasift.exceptions.DataSiftApiException`, :class:`requests.exceptions.HTTPError` """


        params = {}

        if label:
            params['label'] = label
        if status:
            params['status'] = status
        if master:
            params['master'] = master

        return self.request.put(str(id), params)