Add RAG input types (#12684)

Co-authored-by: Erick Friis <erick@langchain.dev>

templates/rag-semi-structured/rag_semi_structured/chain.py

@@ -4,6 +4,7 @@ import uuid
 from langchain.chat_models import ChatOpenAI
 from langchain.embeddings import OpenAIEmbeddings
 from langchain.prompts import ChatPromptTemplate
+from langchain.pydantic_v1 import BaseModel
 from langchain.retrievers.multi_vector import MultiVectorRetriever
 from langchain.schema.document import Document
 from langchain.schema.output_parser import StrOutputParser
@@ -109,3 +110,11 @@ chain = (
     | model
     | StrOutputParser()
 )
+
+
+# Add typing for input
+class Question(BaseModel):
+    __root__: str
+
+
+chain = chain.with_types(input_type=Question)