code: def get_objective_bank_hierarchy_design_session(self):
          
          if not self.supports_objective_bank_hierarchy_design():
              raise Unimplemented()
          try:
              from . import sessions
          except ImportError:
              raise OperationFailed()
          try:
              session = sessions.ObjectiveBankHierarchyDesignSession(runtime=self._runtime)
          except AttributeError:
              raise OperationFailed()
          return session
docs: Gets the session designing objective bank hierarchies.
  
          return: (osid.learning.ObjectiveBankHierarchyDesignSession) - an
                  ObjectiveBankHierarchyDesignSession
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented -
                  supports_objective_bank_hierarchy_design() is false
          compliance: optional - This method must be implemented if
                      supports_objective_bank_hierarchy_design() is true.