[experimental][llms][OllamaFunctions] tool calling related fixes (#22339)

Fixes issues with tool calling to handle tool objects correctly. Added
support to handle ToolMessage correctly.
Added additional checks for error conditions.

---------

Co-authored-by: ccurme <chester.curme@gmail.com>

libs/experimental/tests/integration_tests/llms/test_ollama_functions.py

@@ -2,6 +2,8 @@
 
 import unittest
 
+from langchain_community.tools import DuckDuckGoSearchResults
+from langchain_community.tools.pubmed.tool import PubmedQueryRun
 from langchain_core.messages import AIMessage
 from langchain_core.pydantic_v1 import BaseModel, Field
 
@@ -22,7 +24,7 @@ class TestOllamaFunctions(unittest.TestCase):
     """
 
     def test_default_ollama_functions(self) -> None:
-        base_model = OllamaFunctions(model="llama3", format="json")
+        base_model = OllamaFunctions(model="phi3", format="json")
 
         # bind functions
         model = base_model.bind_tools(
@@ -60,8 +62,22 @@ class TestOllamaFunctions(unittest.TestCase):
         assert tool_call
         self.assertEqual("get_current_weather", tool_call.get("name"))
 
+    def test_ollama_functions_tools(self) -> None:
+        base_model = OllamaFunctions(model="phi3", format="json")
+        model = base_model.bind_tools(
+            tools=[PubmedQueryRun(), DuckDuckGoSearchResults(max_results=2)]
+        )
+        res = model.invoke("What causes lung cancer?")
+        self.assertIsInstance(res, AIMessage)
+        res = AIMessage(**res.__dict__)
+        tool_calls = res.tool_calls
+        assert tool_calls
+        tool_call = tool_calls[0]
+        assert tool_call
+        self.assertEqual("pub_med", tool_call.get("name"))
+
     def test_default_ollama_functions_default_response(self) -> None:
-        base_model = OllamaFunctions(model="llama3", format="json")
+        base_model = OllamaFunctions(model="phi3", format="json")
 
         # bind functions
         model = base_model.bind_tools(