code: def get_agents_by_resource(self, resource_id):
          
          agent_list = []
          for agent_id in self.get_agent_ids_by_resource(resource_id):
              agent_list.append(Agent(agent_id))
          return AgentList(agent_list)
docs: Gets the list of ``Agents`` mapped to a ``Resource``.
  
          arg:    resource_id (osid.id.Id): ``Id`` of a ``Resource``
          return: (osid.authentication.AgentList) - list of agents
          raise:  NotFound - ``resource_id`` is not found
          raise:  NullArgument - ``resource_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*