docs: def get_relationship(self, relationship_id):
          """Gets the ``Relationship`` specified by its ``Id``.
  
          arg:    relationship_id (osid.id.Id): the ``Id`` of the
                  ``Relationship`` to retrieve
          return: (osid.relationship.Relationship) - the returned
                  ``Relationship``
          raise:  NotFound - no ``Relationship`` found with the given
                  ``Id``
          raise:  NullArgument - ``relationship_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for
          # osid.resource.ResourceLookupSession.get_resource
          # NOTE: This implementation currently ignores plenary view
          collection = JSONClientValidated('relationship',
                                           collection='Relationship',
                                           runtime=self._runtime)
          result = collection.find_one(
              dict({'_id': ObjectId(self._get_id(relationship_id, 'relationship').get_identifier())},
                   **self._view_filter()))
          return objects.Relationship(osid_object_map=result, runtime=self._runtime, proxy=self._proxy)