def assign_equivalent_objective(self, objective_id=None, equivalent_objective_id=None):
raise Unimplemented()<EOL>
Makes an objective equivalent to another objective for the
        purposes of satisfying a requisite.

        arg:    objective_id (osid.id.Id): the Id of the principal
                Objective
        arg:    equivalent_objective_id (osid.id.Id): the Id of the
                equivalent Objective
        raise:  AlreadyExists - objective_id already mapped to
                equiavelnt_objective_id
        raise:  NotFound - objective_id or equivalent_objective_id not
                found
        raise:  NullArgument - objective_id or equivalent_objective_id
                is null
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        compliance: mandatory - This method must be implemented.