Refactor dimension index sequence

Author: CPBridge

src/highdicom/__init__.py

@@ -61,6 +61,7 @@
 )
 from highdicom import frame
 from highdicom.image import (
+    DimensionIndexSequence,
     Image,
     imread,
     get_volume_from_series,
@@ -89,6 +90,7 @@
     'ContentQualificationValues',
     'ContributingEquipment',
     'CoordinateSystemNames',
+    'DimensionIndexSequence',
     'DimensionOrganizationTypeValues',
     'Image',
     'InterpolationMethods',

src/highdicom/_module_utils.py

@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any, Dict, List, Optional, Union
+from typing import Any
 from collections.abc import Sequence
 
 from pydicom import Dataset