LangChain Expression LanguageCookbookCode writingCode writingExample of how to use LCEL to write Python code.from langchain.chat_models import ChatOpenAIfrom langchain.prompts import ChatPromptTemplate, SystemMessagePromptTemplate, HumanMessagePromptTemplatefrom langchain.schema.output_parser import StrOutputParserfrom langchain.utilities import PythonREPLtemplate = """Write some python code to solve the user's problem. Return only python code in Markdown format, e.g.:```python....```"""prompt = ChatPromptTemplate.from_messages(    [("system", template), ("human", "{input}")])model = ChatOpenAI()def _sanitize_output(text: str):    _, after = text.split("```python")    return after.split("```")[0]chain = prompt | model | StrOutputParser() | _sanitize_output | PythonREPL().runchain.invoke({"input": "whats 2 plus 2"})    Python REPL can execute arbitrary code. Use with caution.    '4\n'PreviousAgentsNextAdding memory