OpenAI function calling support (#1011)

docs/components/llms.mdx

@@ -60,9 +60,129 @@ llm:
     top_p: 1
     stream: false
 ```
-
 </CodeGroup>
 
+### Function Calling
+To enable [function calling](https://platform.openai.com/docs/guides/function-calling) in your application using embedchain and OpenAI, you need to pass functions into `OpenAILlm` class as an array of functions. Here are several ways in which you can achieve that:
+
+Examples:
+<Accordion title="Using Pydantic Models">
+  ```python
+import os
+from embedchain import Pipeline as App
+from embedchain.llm.openai import OpenAILlm
+import requests
+from pydantic import BaseModel, Field, ValidationError, field_validator
+
+os.environ["OPENAI_API_KEY"] = "sk-xxx"
+
+class QA(BaseModel):
+    """
+    A question and answer pair.
+    """
+
+    question: str = Field(
+        ..., description="The question.", example="What is a mountain?"
+    )
+    answer: str = Field(
+        ..., description="The answer.", example="A mountain is a hill."
+    )
+    person_who_is_asking: str = Field(
+        ..., description="The person who is asking the question.", example="John"
+    )
+
+    @field_validator("question")
+    def question_must_end_with_a_question_mark(cls, v):
+        """
+        Validate that the question ends with a question mark.
+        """
+        if not v.endswith("?"):
+            raise ValueError("question must end with a question mark")
+        return v
+
+    @field_validator("answer")
+    def answer_must_end_with_a_period(cls, v):
+        """
+        Validate that the answer ends with a period.
+        """
+        if not v.endswith("."):
+            raise ValueError("answer must end with a period")
+        return v
+
+llm = OpenAILlm(config=None,functions=[QA])
+app = App(llm=llm)
+
+result = app.query("Hey I am Sid. What is a mountain? A mountain is a hill.")
+
+print(result)
+  ```
+  </Accordion>
+  
+  <Accordion title="Using OpenAI JSON schema">
+```python
+import os
+from embedchain import Pipeline as App
+from embedchain.llm.openai import OpenAILlm
+import requests
+from pydantic import BaseModel, Field, ValidationError, field_validator
+
+os.environ["OPENAI_API_KEY"] = "sk-xxx"
+
+json_schema = {
+    "name": "get_qa",
+    "description": "A question and answer pair and the user who is asking the question.",
+    "parameters": {
+        "type": "object",
+        "properties": {
+            "question": {"type": "string", "description": "The question."},
+            "answer": {"type": "string", "description": "The answer."},
+            "person_who_is_asking": {
+                "type": "string",
+                "description": "The person who is asking the question.",
+            }
+        },
+        "required": ["question", "answer", "person_who_is_asking"],
+    },
+}
+
+llm = OpenAILlm(config=None,functions=[json_schema])
+app = App(llm=llm)
+
+result = app.query("Hey I am Sid. What is a mountain? A mountain is a hill.")
+
+print(result)
+  ```
+  </Accordion>
+  <Accordion title="Using actual python functions">
+  ```python
+import os
+from embedchain import Pipeline as App
+from embedchain.llm.openai import OpenAILlm
+import requests
+from pydantic import BaseModel, Field, ValidationError, field_validator
+
+os.environ["OPENAI_API_KEY"] = "sk-xxx"
+
+def find_info_of_pokemon(pokemon: str):
+    """
+    Find the information of the given pokemon.
+    Args:
+        pokemon: The pokemon.
+    """
+    req = requests.get(f"https://pokeapi.co/api/v2/pokemon/{pokemon}")
+    if req.status_code == 404:
+        raise ValueError("pokemon not found")
+    return req.json()
+
+llm = OpenAILlm(config=None,functions=[find_info_of_pokemon])
+app = App(llm=llm)
+
+result = app.query("Tell me more about the pokemon pikachu.")
+
+print(result)
+```
+</Accordion>
+
 ## Google AI
 
 To use Google AI model, you have to set the `GOOGLE_API_KEY` environment variable. You can obtain the Google API key from the [Google Maker Suite](https://makersuite.google.com/app/apikey)