code: def get_activity_objective_bank_session(self, proxy):
          
          if not self.supports_activity_objective_bank():
              raise Unimplemented()
          try:
              from . import sessions
          except ImportError:
              raise OperationFailed()
          proxy = self._convert_proxy(proxy)
          try:
              session = sessions.ActivityObjectiveBankSession(proxy=proxy, runtime=self._runtime)
          except AttributeError:
              raise OperationFailed()
          return session
docs: Gets the session for retrieving activity to objective bank mappings.
  
          :param proxy: a proxy
          :type proxy: ``osid.proxy.Proxy``
          :return: an ``ActivityObjectiveBankSession``
          :rtype: ``osid.learning.ActivityObjectiveBankSession``
          :raise: ``NullArgument`` -- ``proxy`` is ``null``
          :raise: ``OperationFailed`` -- unable to complete request
          :raise: ``Unimplemented`` -- ``supports_activity_objective_bank()`` is ``false``
  
          *compliance: optional -- This method must be implemented if ``supports_activity_objective_bank()`` is ``true``.*