core[patch]: Add TypeError handler into get_graph of Runnable (#19856)

# Description

## Problem

`Runnable.get_graph` fails when `InputType` or `OutputType` property
raises `TypeError`.

-
003c98e5b4/libs/core/langchain_core/runnables/base.py (L250-L274)
-
003c98e5b4/libs/core/langchain_core/runnables/base.py (L394-L396)

This problem prevents getting a graph of `Runnable` objects whose
`InputType` or `OutputType` property raises `TypeError` but whose
`invoke` works well, such as `langchain.output_parsers.RegexParser`,
which I have already pointed out in #19792 that a `TypeError` would
occur.

## Solution

- Add `try-except` syntax to handle `TypeError` to the codes which get
`input_node` and `output_node`.

# Issue
- #19801 

# Twitter Handle
- [hmdev3](https://twitter.com/hmdev3)

---------

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

libs/core/langchain_core/runnables/base.py

@@ -391,9 +391,15 @@ class Runnable(Generic[Input, Output], ABC):
         from langchain_core.runnables.graph import Graph
 
         graph = Graph()
-        input_node = graph.add_node(self.get_input_schema(config))
+        try:
+            input_node = graph.add_node(self.get_input_schema(config))
+        except TypeError:
+            input_node = graph.add_node(create_model(self.get_name("Input")))
         runnable_node = graph.add_node(self)
-        output_node = graph.add_node(self.get_output_schema(config))
+        try:
+            output_node = graph.add_node(self.get_output_schema(config))
+        except TypeError:
+            output_node = graph.add_node(create_model(self.get_name("Output")))
         graph.add_edge(input_node, runnable_node)
         graph.add_edge(runnable_node, output_node)
         return graph

libs/core/tests/unit_tests/runnables/test_graph.py

@@ -1,3 +1,5 @@
+from typing import Optional
+
 from syrupy import SnapshotAssertion
 
 from langchain_core.language_models import FakeListLLM
@@ -5,7 +7,7 @@ from langchain_core.output_parsers.list import CommaSeparatedListOutputParser
 from langchain_core.output_parsers.string import StrOutputParser
 from langchain_core.output_parsers.xml import XMLOutputParser
 from langchain_core.prompts.prompt import PromptTemplate
-from langchain_core.runnables.base import Runnable
+from langchain_core.runnables.base import Runnable, RunnableConfig
 
 
 def test_graph_single_runnable(snapshot: SnapshotAssertion) -> None:
@@ -687,3 +689,47 @@ def test_graph_sequence_map(snapshot: SnapshotAssertion) -> None:
     assert graph.draw_ascii() == snapshot(name="ascii")
     assert graph.draw_mermaid() == snapshot(name="mermaid")
     assert graph.draw_mermaid(with_styles=False) == snapshot(name="mermaid-simple")
+
+
+def test_runnable_get_graph_with_invalid_input_type() -> None:
+    """Test that error isn't raised when getting graph with invalid input type."""
+
+    class InvalidInputTypeRunnable(Runnable[int, int]):
+        @property
+        def InputType(self) -> type:
+            raise TypeError()
+
+        def invoke(
+            self,
+            input: int,
+            config: Optional[RunnableConfig] = None,
+        ) -> int:
+            return input
+
+    runnable = InvalidInputTypeRunnable()
+    # check whether runnable.invoke works
+    assert runnable.invoke(1) == 1
+    # check whether runnable.get_graph works
+    runnable.get_graph()
+
+
+def test_runnable_get_graph_with_invalid_output_type() -> None:
+    """Test that error is't raised when getting graph with invalid output type."""
+
+    class InvalidOutputTypeRunnable(Runnable[int, int]):
+        @property
+        def OutputType(self) -> type:
+            raise TypeError()
+
+        def invoke(
+            self,
+            input: int,
+            config: Optional[RunnableConfig] = None,
+        ) -> int:
+            return input
+
+    runnable = InvalidOutputTypeRunnable()
+    # check whether runnable.invoke works
+    assert runnable.invoke(1) == 1
+    # check whether runnable.get_graph works
+    runnable.get_graph()