[Models] Improve iteration over layers (#19497)

Signed-off-by: Lukas Geiger <lukas.geiger94@gmail.com>

vllm/model_executor/models/gemma.py

@@ -18,6 +18,7 @@
 """Inference-only Gemma model compatible with HuggingFace weights."""
 from collections.abc import Iterable
 from functools import cache
+from itertools import islice
 from typing import Optional, Union
 
 import torch
@@ -308,7 +309,7 @@ class GemmaModel(nn.Module):
         else:
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
-        for layer in self.layers[self.start_layer:self.end_layer]:
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(
                 positions,
                 hidden_states,