@abc.abstractmethod<EOL><INDENT>def create_relationship(self, relationship_form):<DEDENT>
return<EOL>
Creates a new ``Relationship``.

        :param relationship_form: the form for this ``Relationship``
        :type relationship_form: ``osid.relationship.RelationshipForm``
        :return: the new ``Relationship``
        :rtype: ``osid.relationship.Relationship``
        :raise: ``IllegalState`` -- ``relationship_form`` already used in a create transaction
        :raise: ``InvalidArgument`` -- one or more of the form elements is invalid
        :raise: ``NullArgument`` -- ``relationship_form`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure
        :raise: ``Unsupported`` -- ``relationship_form`` did not originate from ``get_relationship_form_for_create()``

        *compliance: mandatory -- This method must be implemented.*