<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _GetSerializedAttributeContainerList(self, container_type):
 """Retrieves a serialized attribute container list. Args: container_type (str):
 attribute container type. Returns: SerializedAttributeContainerList: serialized attribute container list. """

    container_list = self._serialized_attribute_containers.get(
        container_type, None)
    if not container_list:
      container_list = SerializedAttributeContainerList()
      self._serialized_attribute_containers[container_type] = container_list

    return container_list