def update_fax(self, fax_id, payload_fax_modification, **kwargs):  # noqa: E501
        """Modify fax record  # noqa: E501

        You can modify a fax record's comment or mark it as read  # noqa: E501
        This method makes a synchronous HTTP request by default. To make an
        asynchronous HTTP request, please pass async=True
        >>> thread = api.update_fax(fax_id, payload_fax_modification, async=True)
        >>> result = thread.get()

        :param async bool
        :param str fax_id: (required)
        :param PayloadFaxModification payload_fax_modification: (required)
        :return: None
                 If the method is called asynchronously,
                 returns the request thread.
        """
        kwargs['_return_http_data_only'] = True
        if kwargs.get('async'):
            return self.update_fax_with_http_info(fax_id, payload_fax_modification, **kwargs)  # noqa: E501
        else:
            (data) = self.update_fax_with_http_info(fax_id, payload_fax_modification, **kwargs)  # noqa: E501
            return data