code: def add_membership(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')
          response = self._send(http_method='PUT',
                                location_id='3fd2e6ca-fb30-443a-b579-95b19ed0934c',
                                version='5.1-preview.1',
                                route_values=route_values)
          return self._deserialize('GraphMembership', response)
docs: AddMembership.
          [Preview API] Create a new membership between a container and subject.
          :param str subject_descriptor: A descriptor to a group or user that can be the child subject in the relationship.
          :param str container_descriptor: A descriptor to a group that can be the container in the relationship.
          :rtype: :class:`<GraphMembership> <azure.devops.v5_1.graph.models.GraphMembership>`