Check if this datastream has a valid checksum in Fedora, by
        running the :meth:`REST_API.compareDatastreamChecksum` API
        call.  Returns a boolean based on the checksum valid
        response from Fedora.

        :param date: (optional) check the datastream validity at a
            particular date/time (e.g., for versionable datastreams)

def validate_checksum(self, date=None):
        '''Check if this datastream has a valid checksum in Fedora, by
        running the :meth:`REST_API.compareDatastreamChecksum` API
        call.  Returns a boolean based on the checksum valid
        response from Fedora.

        :param date: (optional) check the datastream validity at a
            particular date/time (e.g., for versionable datastreams)
        '''
        r = self.obj.api.compareDatastreamChecksum(self.obj.pid, self.id,
                                                               asOfDateTime=date)
        dsprofile = parse_xml_object(DatastreamProfile, r.content, r.url)
        return dsprofile.checksum_valid