class_docstr: Example messenger onboarding world for Echo task, displays.
  
  onboarding worlds that only exist to send an introduction message.
class_docstr_tok: ["Example","messenger","onboarding","world","for","Echo","task",",","displays",".","onboarding","worlds","that","only","exist","to","send","an","introduction","message","."]
code: def parley(self):
      self.agent.observe(
          {
              "id": "Onboarding",
              "text": "Welcome to the onboarding world for our echo bot. "
              "The next message you send will be echoed. Use [DONE] "
              "to finish the chat.",
          }
      )
      self.episodeDone = True
  
imports: from parlai.core.worlds import World
  from parlai.chat_service.services.messenger.worlds import OnboardWorld
label_desc: Use image node_id 2 for calling the MessengerEchoOnboardWorld obj's underlying member method code with example usage: obj.parley() without return types