feat: add support for multimodal in lora kernels (#2472) [skip ci]

* feat: add support for multimodal in lora kernels

* fix: improve multimodal checks

* fix: add fallback for model config

* chor: add gemma3 to docs

docs/lora_optims.qmd

@@ -17,6 +17,7 @@ We currently support several common model architectures, including (but not limi
 - `qwen2`
 - `gemma`
 - `gemma2`
+- `gemma3`
 
 <details>
 

src/axolotl/monkeypatch/lora_kernels.py

@@ -252,12 +252,38 @@ def apply_lora_kernel_patches(
     LOG.setLevel(logging.INFO)
 
     # Choose activation based on model type
-    activation = model.config.hidden_act
+    activation = None
+    text_config = (
+        model.config.get_text_config()
+        if hasattr(model.config, "get_text_config")
+        else model.config
+    )
+    if hasattr(text_config, "hidden_act"):
+        activation = text_config.hidden_act
+    elif hasattr(text_config, "hidden_activation"):
+        activation = text_config.hidden_activation
+
+    # map activation to supported activation
+    if "gelu" in activation:
+        # gemma3 uses gelu_pytorch_tanh
+        activation = "gelu"
+
     if activation not in SUPPORTED_ACTIVATIONS:
         raise NotImplementedError(f"Activation {activation} is not supported")
 
+    layers = []
+    # check for multimodal models first
+    if hasattr(model, "language_model"):
+        layers = model.language_model.model.layers
+    elif hasattr(model, "model"):
+        layers = model.model.model.layers
+    else:
+        raise NotImplementedError(
+            f"Model type {model.config.model_type} is not supported yet. Please create an Issue."
+        )
+
     # Patch each layer
-    for layer in model.model.model.layers:
+    for layer in layers:
         # Add QKV, O fallback implementations to start
         # These will be overwritten later (if some conditions apply)
         layer.self_attn.apply_qkv = types.MethodType(