model: fix gemma3 with transformers 4.53.1 (#317)

Author: rebel-kblee

src/optimum/rbln/transformers/models/gemma3/modeling_gemma3.py

@@ -408,6 +408,13 @@ def _create_embedding_layer(self):
     def _update_sliding_window_config(cls, model_config: PretrainedConfig, rbln_config: RBLNGemma3ForCausalLMConfig):
         sliding_window = getattr(model_config, "sliding_window", None)
         sliding_window_pattern = getattr(model_config, "sliding_window_pattern", None)
+        if sliding_window_pattern is None:
+            if hasattr(model_config, "layer_types"):
+                first_full_attention_index = model_config.layer_types.index("full_attention")
+                sliding_window_pattern = first_full_attention_index + 1
+            else:
+                raise ValueError("Cannot determine sliding_window_pattern from model_config")
+
         if sliding_window_pattern <= model_config.num_hidden_layers:
             rbln_config.cache_impl = "hybrid"
             rbln_config.sliding_window = sliding_window