feat: move lora into mlx-lm (#337)

* feat: Add lora and qlora training to mlx-lm


---------

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

llms/mlx_lm/tuner/utils.py

@@ -0,0 +1,22 @@
+import mlx.core as mx
+from mlx.utils import tree_unflatten
+
+from .lora import LoRALinear
+
+
+def apply_lora_layers(model, adapter_file: str):
+    adapters = list(mx.load(adapter_file).items())
+    linear_replacements = {}
+    lora_layers = set(
+        [name.replace(".lora_a", "").replace(".lora_b", "") for name, _ in adapters]
+    )
+
+    for name, module in model.named_modules():
+        if name in lora_layers:
+            replacement_module = LoRALinear.from_linear(module)
+            linear_replacements[name] = replacement_module
+
+    model.update_modules(tree_unflatten(list(linear_replacements.items())))
+
+    model.update(tree_unflatten(adapters))
+    return model