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>`

def add_membership(self, subject_descriptor, container_descriptor):
        """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>`
        """
        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)