LoRA: support tools(function calling) format datasets (#995)

* LoRA: support fine-tuning tools datasets

* LoRA: Split small function

* LoRA: add tools format to lora docs

* LoRA: pre-commit fix

* Revert "LoRA: pre-commit fix"

This reverts commit b94b7e0fe7.

* Revert "LoRA: Split small function"

This reverts commit 3f6a5f19fd.

* LoRA: remove ToolsDataset

In a JSONL file, not all data is required to include the tools value.

* nit in readme

* nit in readme

* nit in readme

---------

Co-authored-by: Awni Hannun <awni@apple.com>

llms/mlx_lm/LORA.md

@@ -160,8 +160,8 @@ For fine-tuning (`--train`), the data loader expects a `train.jsonl` and a
 `valid.jsonl` to be in the data directory. For evaluation (`--test`), the data
 loader expects a `test.jsonl` in the data directory. 
 
-Currently, `*.jsonl` files support three data formats: `chat`,
-`completions`, and `text`. Here are three examples of these formats:
+Currently, `*.jsonl` files support `chat`, `tools`, `completions`, and `text`
+data formats. Here are examples of these formats:
 
 `chat`:
 
@@ -169,6 +169,58 @@ Currently, `*.jsonl` files support three data formats: `chat`,
 {"messages": [{"role": "system", "content": "You are a helpful assistant."}, {"role": "user", "content": "Hello."}, {"role": "assistant", "content": "How can I assistant you today."}]}
 ```
 
+`tools`:
+
+```jsonl
+{"messages":[{"role":"user","content":"What is the weather in San Francisco?"},{"role":"assistant","tool_calls":[{"id":"call_id","type":"function","function":{"name":"get_current_weather","arguments":"{\"location\": \"San Francisco, USA\", \"format\": \"celsius\"}"}}]}],"tools":[{"type":"function","function":{"name":"get_current_weather","description":"Get the current weather","parameters":{"type":"object","properties":{"location":{"type":"string","description":"The city and country, eg. San Francisco, USA"},"format":{"type":"string","enum":["celsius","fahrenheit"]}},"required":["location","format"]}}}]}
+```
+
+<details>
+<summary>View the expanded single data tool format</summary>
+
+```jsonl
+{
+    "messages": [
+        { "role": "user", "content": "What is the weather in San Francisco?" },
+        {
+            "role": "assistant",
+            "tool_calls": [
+                {
+                    "id": "call_id",
+                    "type": "function",
+                    "function": {
+                        "name": "get_current_weather",
+                        "arguments": "{\"location\": \"San Francisco, USA\", \"format\": \"celsius\"}"
+                    }
+                }
+            ]
+        }
+    ],
+    "tools": [
+        {
+            "type": "function",
+            "function": {
+                "name": "get_current_weather",
+                "description": "Get the current weather",
+                "parameters": {
+                    "type": "object",
+                    "properties": {
+                        "location": {
+                            "type": "string",
+                            "description": "The city and country, eg. San Francisco, USA"
+                        },
+                        "format": { "type": "string", "enum": ["celsius", "fahrenheit"] }
+                    },
+                    "required": ["location", "format"]
+                }
+            }
+        }
+    ]
+}
+```
+
+</details>
+
 `completions`:
 
 ```jsonl
@@ -215,11 +267,13 @@ hf_dataset:
 - Arguments specified in `config` will be passed as keyword arguments to
   [`datasets.load_dataset`](https://huggingface.co/docs/datasets/v2.20.0/en/package_reference/loading_methods#datasets.load_dataset).
 
-In general, for the `chat` and `completions` formats, Hugging Face [chat
-templates](https://huggingface.co/blog/chat-templates) are used. This applies
-the model's chat template by default. If the model does not have a chat
-template, then Hugging Face will use a default. For example, the final text in
-the `chat` example above with Hugging Face's default template becomes:
+In general, for the `chat`, `tools` and `completions` formats, Hugging Face
+[chat
+templates](https://huggingface.co/docs/transformers/main/en/chat_templating)
+are used. This applies the model's chat template by default. If the model does
+not have a chat template, then Hugging Face will use a default. For example,
+the final text in the `chat` example above with Hugging Face's default template
+becomes:
 
 ```text
 <|im_start|>system

llms/mlx_lm/tuner/datasets.py

@@ -36,7 +36,10 @@ class ChatDataset(Dataset):
     def __getitem__(self, idx: int):
         messages = self._data[idx]["messages"]
         text = self._tokenizer.apply_chat_template(
-            messages, tokenize=False, add_generation_prompt=True
+            messages,
+            tools=self._data[idx].get("tools", None),
+            tokenize=False,
+            add_generation_prompt=True,
         )
         return text
 

llms/mlx_lm/tuner/trainer.py

@@ -93,9 +93,7 @@ def iterate_batches(dataset, tokenizer, batch_size, max_seq_length, train=False)
             # Encode batch
             batch = [tokenizer.encode(dataset[j]) for j in batch_idx[i]]
             for b in batch:
-                if b[-1] == tokenizer.eos_token_id:
-                    print("[WARNING] Example already has an EOS token appended")
-                else:
+                if b[-1] != tokenizer.eos_token_id:
                     b.append(tokenizer.eos_token_id)
 
             lengths = [len(x) for x in batch]