code: def get_learning_path_session_for_objective_bank(self, objective_bank_id=None):
          
          if not objective_bank_id:
              raise NullArgument
          if not self.supports_learning_path():
              raise Unimplemented()
          try:
              from . import sessions
          except ImportError:
              raise OperationFailed()
          try:
              session = sessions.LearningPathSession(objective_bank_id, runtime=self._runtime)
          except AttributeError:
              raise OperationFailed()
          return session
docs: Gets the OsidSession associated with the learning path service
          for the given objective bank.
  
          arg:    objectiveBankId (osid.id.Id): the Id of the
                  ObjectiveBank
          return: (osid.learning.LearningPathSession) - a
                  LearningPathSession
          raise:  NotFound - no objective bank found by the given Id
          raise:  NullArgument - objectiveBankId is null
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - supporty_learning_path() or
                  supports_visible_federation() is false
          compliance: optional - This method must be implemented if
                      supports_learning_path() and
                      supports_visible_federation() are true