langchain[patch], experimental[minor]: Adds OllamaFunctions wrapper (#13330)

CC @baskaryan @hwchase17 @jmorganca 

Having a bit of trouble importing `langchain_experimental` from a
notebook, will figure it out tomorrow

~Ah and also is blocked by #13226~

---------

Co-authored-by: Lance Martin <lance@langchain.dev>
Co-authored-by: Bagatur <baskaryan@gmail.com>

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

@@ -0,0 +1,49 @@
+"""Test OllamaFunctions"""
+
+import unittest
+
+from langchain.chat_models.ollama import ChatOllama
+
+from langchain_experimental.llms.ollama_functions import OllamaFunctions
+
+
+class TestOllamaFunctions(unittest.TestCase):
+    """
+    Test OllamaFunctions
+    """
+
+    def test_default_ollama_functions(self) -> None:
+        base_model = OllamaFunctions(model="mistral")
+        self.assertIsInstance(base_model.model, ChatOllama)
+
+        # bind functions
+        model = base_model.bind(
+            functions=[
+                {
+                    "name": "get_current_weather",
+                    "description": "Get the current weather in a given location",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {
+                            "location": {
+                                "type": "string",
+                                "description": "The city and state, "
+                                "e.g. San Francisco, CA",
+                            },
+                            "unit": {
+                                "type": "string",
+                                "enum": ["celsius", "fahrenheit"],
+                            },
+                        },
+                        "required": ["location"],
+                    },
+                }
+            ],
+            function_call={"name": "get_current_weather"},
+        )
+
+        res = model.invoke("What's the weather in San Francisco?")
+
+        function_call = res.additional_kwargs.get("function_call")
+        assert function_call
+        self.assertEqual(function_call.get("name"), "get_current_weather")