[Models] Improve iteration over layers (#26425)

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

vllm/model_executor/models/longcat_flash.py

@@ -35,6 +35,7 @@
 
 import typing
 from collections.abc import Callable, Iterable
+from itertools import islice
 from typing import Optional, Union
 
 import torch
@@ -519,8 +520,7 @@ class FlashModel(nn.Module):
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
 
-        for i in range(self.start_layer, self.end_layer):
-            layer = self.layers[i]
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(
                 positions,
                 hidden_states,