chore: import upstream snapshot with attribution

tests/langchain/sample_code/simple_runnable.py

@@ -0,0 +1,14 @@
+from langchain_core.output_parsers import StrOutputParser
+from langchain_core.prompts import PromptTemplate
+from langchain_openai import ChatOpenAI
+
+import mlflow
+
+prompt = PromptTemplate(
+    input_variables=["product"],
+    template="What is {product}?",
+)
+llm = ChatOpenAI(temperature=0.1, stream_usage=True)
+chain = prompt | llm | StrOutputParser()
+
+mlflow.models.set_model(chain)