Use a less specific return type for | on Runnables (#11762)

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---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/langchain/langchain/chains/sql_database/query.py

@@ -4,7 +4,7 @@ from langchain.chains.sql_database.prompt import PROMPT, SQL_PROMPTS
 from langchain.schema.language_model import BaseLanguageModel
 from langchain.schema.output_parser import NoOpOutputParser
 from langchain.schema.prompt_template import BasePromptTemplate
-from langchain.schema.runnable import RunnableParallel, RunnableSequence
+from langchain.schema.runnable import Runnable, RunnableParallel
 from langchain.utilities.sql_database import SQLDatabase
 
 
@@ -30,7 +30,7 @@ def create_sql_query_chain(
     db: SQLDatabase,
     prompt: Optional[BasePromptTemplate] = None,
     k: int = 5,
-) -> RunnableSequence[Union[SQLInput, SQLInputWithTables], str]:
+) -> Runnable[Union[SQLInput, SQLInputWithTables], str]:
     """Create a chain that generates SQL queries.
 
     Args:

libs/langchain/langchain/schema/runnable/base.py

@@ -242,7 +242,7 @@ class Runnable(Generic[Input, Output], ABC):
             Callable[[Iterator[Any]], Iterator[Other]],
             Mapping[str, Union[Runnable[Any, Other], Callable[[Any], Other], Any]],
         ],
-    ) -> RunnableSequence[Input, Other]:
+    ) -> Runnable[Input, Other]:
         """Compose this runnable with another object to create a RunnableSequence."""
         return RunnableSequence(first=self, last=coerce_to_runnable(other))
 
@@ -254,7 +254,7 @@ class Runnable(Generic[Input, Output], ABC):
             Callable[[Iterator[Other]], Iterator[Any]],
             Mapping[str, Union[Runnable[Other, Any], Callable[[Other], Any], Any]],
         ],
-    ) -> RunnableSequence[Other, Output]:
+    ) -> Runnable[Other, Output]:
         """Compose this runnable with another object to create a RunnableSequence."""
         return RunnableSequence(first=coerce_to_runnable(other), last=self)
 
@@ -1064,7 +1064,7 @@ class RunnableSequence(RunnableSerializable[Input, Output]):
             Callable[[Iterator[Any]], Iterator[Other]],
             Mapping[str, Union[Runnable[Any, Other], Callable[[Any], Other], Any]],
         ],
-    ) -> RunnableSequence[Input, Other]:
+    ) -> Runnable[Input, Other]:
         if isinstance(other, RunnableSequence):
             return RunnableSequence(
                 first=self.first,
@@ -1086,7 +1086,7 @@ class RunnableSequence(RunnableSerializable[Input, Output]):
             Callable[[Iterator[Other]], Iterator[Any]],
             Mapping[str, Union[Runnable[Other, Any], Callable[[Other], Any], Any]],
         ],
-    ) -> RunnableSequence[Other, Output]:
+    ) -> Runnable[Other, Output]:
         if isinstance(other, RunnableSequence):
             return RunnableSequence(
                 first=other.first,

libs/langchain/tests/unit_tests/schema/runnable/test_locals.py

@@ -7,6 +7,7 @@ from langchain.prompts import PromptTemplate
 from langchain.schema.runnable import (
     GetLocalVar,
     PutLocalVar,
+    Runnable,
     RunnablePassthrough,
     RunnableSequence,
 )
@@ -52,12 +53,12 @@ def test_incorrect_usage(runnable: RunnableSequence, error: Type[Exception]) ->
 
 
 def test_get_in_map() -> None:
-    runnable: RunnableSequence = PutLocalVar("input") | {"bar": GetLocalVar("input")}
+    runnable: Runnable = PutLocalVar("input") | {"bar": GetLocalVar("input")}
     assert runnable.invoke("foo") == {"bar": "foo"}
 
 
 def test_put_in_map() -> None:
-    runnable: RunnableSequence = {"bar": PutLocalVar("input")} | GetLocalVar("input")
+    runnable: Runnable = {"bar": PutLocalVar("input")} | GetLocalVar("input")
     with pytest.raises(KeyError):
         runnable.invoke("foo")
 

libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py

@@ -1978,7 +1978,7 @@ def test_combining_sequences(
         lambda x: {"question": x[0] + x[1]}
     )
 
-    chain2 = input_formatter | prompt2 | chat2 | parser2
+    chain2 = cast(RunnableSequence, input_formatter | prompt2 | chat2 | parser2)
 
     assert isinstance(chain, RunnableSequence)
     assert chain2.first == input_formatter
@@ -1987,7 +1987,7 @@ def test_combining_sequences(
     if sys.version_info >= (3, 9):
         assert dumps(chain2, pretty=True) == snapshot
 
-    combined_chain = chain | chain2
+    combined_chain = cast(RunnableSequence, chain | chain2)
 
     assert combined_chain.first == prompt
     assert combined_chain.middle == [
@@ -2972,7 +2972,7 @@ def llm_with_multi_fallbacks() -> RunnableWithFallbacks:
 
 
 @pytest.fixture()
-def llm_chain_with_fallbacks() -> RunnableSequence:
+def llm_chain_with_fallbacks() -> Runnable:
     error_llm = FakeListLLM(responses=["foo"], i=1)
     pass_llm = FakeListLLM(responses=["bar"])