code: def check_membership_existence(self, subject_descriptor, container_descriptor):
          
          route_values = {}
          if subject_descriptor is not None:
              route_values['subjectDescriptor'] = self._serialize.url('subject_descriptor', subject_descriptor, 'str')
          if container_descriptor is not None:
              route_values['containerDescriptor'] = self._serialize.url('container_descriptor', container_descriptor, 'str')
          self._send(http_method='HEAD',
                     location_id='3fd2e6ca-fb30-443a-b579-95b19ed0934c',
                     version='5.1-preview.1',
                     route_values=route_values)
docs: CheckMembershipExistence.
          [Preview API] Check to see if a membership relationship between a container and subject exists.
          :param str subject_descriptor: The group or user that is a child subject of the relationship.
          :param str container_descriptor: The group that is the container in the relationship.