[Model] Extend collect_children and no_init_weights contexts (#32757)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/utils/collection_utils.py

@@ -7,10 +7,10 @@ This is similar in concept to the `collections` module.
 """
 
 from collections import defaultdict
-from collections.abc import Callable, Generator, Hashable, Iterable, Mapping
+from collections.abc import Callable, Generator, Hashable, Iterable, Mapping, Sequence
 from typing import Generic, Literal, TypeVar
 
-from typing_extensions import TypeIs, assert_never
+from typing_extensions import TypeIs, assert_never, overload
 
 T = TypeVar("T")
 
@@ -74,6 +74,34 @@ def is_list_of(
     assert_never(check)
 
 
+@overload
+def common_prefix(items: Sequence[str]) -> str: ...
+
+
+@overload
+def common_prefix(items: Sequence[Sequence[T]]) -> Sequence[T]: ...
+
+
+def common_prefix(items: Sequence[Sequence[T] | str]) -> Sequence[T] | str:
+    """Find the longest prefix common to all items."""
+    if len(items) == 0:
+        return []
+    if len(items) == 1:
+        return items[0]
+
+    shortest = min(items, key=len)
+    if not shortest:
+        return shortest[:0]
+
+    for match_len in range(1, len(shortest) + 1):
+        match = shortest[:match_len]
+        for item in items:
+            if item[:match_len] != match:
+                return shortest[: match_len - 1]
+
+    return shortest
+
+
 def chunk_list(lst: list[T], chunk_size: int) -> Generator[list[T]]:
     """Yield successive chunk_size chunks from lst."""
     for i in range(0, len(lst), chunk_size):