构建LangChain应用出现的TypeError错误

在阅读LangChain官网给出的一些案列时，实际运行却报错，案列代码如下：

from langchain.prompts import ChatPromptTemplate
from langchain_community.chat_models import ChatOpenAI
from langchain_core.output_parsers import StrOutputParser

prompt = ChatPromptTemplate.from_template("tell me a short joke about {topic}")
model = ChatOpenAI()
output_parser = StrOutputParser()

chain = prompt | model | output_parser

chain.invoke({
   "topic": "ice cream"})

错误1：TypeError: Expected a Runnable, callable or dict.Instead got an unsupported type: <class ‘langchain_core.output_parsers.string.StrOutputParser’>

完整报错信息如下：

Traceback (most recent call last):
  File "~/PycharmProjects/LangChain/main.py", line 14,