runnable.bind().bind() should combine kwargs, instead of nesting wrappers (#8467)

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---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

libs/langchain/langchain/schema/runnable.py

@@ -714,6 +714,9 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     def lc_serializable(self) -> bool:
         return True
 
+    def bind(self, **kwargs: Any) -> Runnable[Input, Output]:
+        return self.__class__(bound=self.bound, kwargs={**self.kwargs, **kwargs})
+
     def invoke(self, input: Input, config: Optional[RunnableConfig] = None) -> Output:
         return self.bound.invoke(input, config, **self.kwargs)
 

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

@@ -11,7 +11,7 @@ from langchain.callbacks.tracers.base import BaseTracer
 from langchain.callbacks.tracers.schemas import Run
 from langchain.chat_models.fake import FakeListChatModel
 from langchain.llms.fake import FakeListLLM
-from langchain.load.dump import dumps
+from langchain.load.dump import dumpd, dumps
 from langchain.output_parsers.list import CommaSeparatedListOutputParser
 from langchain.prompts.chat import (
     ChatPromptTemplate,
@@ -609,3 +609,13 @@ def test_seq_prompt_map(
         ]
     )
     assert tracer.runs == snapshot
+
+
+def test_bind_bind() -> None:
+    llm = FakeListLLM(responses=["i'm a textbot"])
+
+    assert dumpd(
+        llm.bind(stop=["Thought:"], one="two").bind(
+            stop=["Observation:"], hello="world"
+        )
+    ) == dumpd(llm.bind(stop=["Observation:"], one="two", hello="world"))