Use builtin KeysView, ValueView, ItemsView

src/scippnexus/base.py

@@ -5,7 +5,7 @@
 
 import inspect
 import warnings
-from collections.abc import Iterator, Mapping
+from collections.abc import ItemsView, Iterator, KeysView, Mapping, ValuesView
 from functools import lru_cache
 from pathlib import PurePosixPath
 from types import MappingProxyType
@@ -287,6 +287,18 @@ def __len__(self) -> int:
     def __iter__(self) -> Iterator[str]:
         return self._children.__iter__()
 
+    def keys(self) -> KeysView[str]:
+        """Return a view of the keys of the group's elements."""
+        return self._children.keys()
+
+    def values(self) -> ValuesView[Field | Group]:
+        """Return a view of the group's elements."""
+        return self._children.values()
+
+    def items(self) -> ItemsView[str, Field | Group]:
+        """Return a view of pairs of the keys and the group's elements."""
+        return self._children.items()
+
     def _get_children_by_nx_class(
         self, select: type | list[type]
     ) -> dict[str, NXobject | Field]:

src/scippnexus/typing.py

@@ -3,7 +3,7 @@
 # @author Simon Heybrock
 from __future__ import annotations
 
-from collections.abc import Callable, Mapping
+from collections.abc import Callable, KeysView, Mapping
 from typing import TYPE_CHECKING, Any, Protocol
 
 
@@ -47,7 +47,7 @@ class H5Group(H5Base, Protocol):
     def __getitem__(self, index: str | Any) -> H5Dataset | H5Group:
         """Keys in the group"""
 
-    def keys(self) -> list[str]:
+    def keys(self) -> KeysView[str]:
         """Keys in the group"""
 
     def create_dataset(self) -> H5Dataset: