Remove typing_extensions (was Py 3.7 compat)

pyproject.toml

@@ -34,7 +34,6 @@ dependencies = [
   "platformdirs >= 4.1",
   "python-dateutil",
   "requests >= 2.7",
-  "typing_extensions",
 ]
 
 [project.optional-dependencies]

sdmx/format/__init__.py

@@ -2,12 +2,7 @@
 from dataclasses import InitVar, dataclass, field
 from enum import Enum, IntFlag
 from functools import lru_cache
-from typing import List, Optional, Union
-
-try:
-    from typing import Literal
-except ImportError:  # Python 3.7
-    from typing_extensions import Literal  # type: ignore
+from typing import List, Literal, Optional, Union
 
 from sdmx.util import parse_content_type
 
@@ -26,7 +21,8 @@
 Flag = IntFlag("Flag", "data meta ss ts")
 f = Flag
 
-#: SDMX standard versions.
+#: SDMX standard versions. In this enumeration, the strings "3.0.0" and "3.0" evaluate
+#: to the same member.
 Version = Enum(
     "Version",
     {"1.0.0": 1, "2.0.0": 2, "2.1": 2.1, "3.0.0": 3, "3.0": 3, "unknown": None},