Remove unused pystac.validation import

This takes 23 000us to import on
a Ryzen 9950X3D, and the import
does not seem to be used after
PR #591 was merged.

Author: pjonsson

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- Remove unused pystac.validation import ([#1583](https://github.com/stac-utils/pystac/pull/1583))
+
 ## [v1.14.1] - 2025-09-18
 
 ### Fixed

pystac/__init__.py

@@ -86,7 +86,6 @@
 from pystac.item_collection import ItemCollection
 from pystac.provider import ProviderRole, Provider
 from pystac.utils import HREF
-import pystac.validation
 
 import pystac.extensions.hooks
 import pystac.extensions.classification
@@ -239,3 +238,18 @@ def read_dict(
     if stac_io is None:
         stac_io = StacIO.default()
     return stac_io.stac_object_from_dict(d, href, root)
+
+
+def __getattr__(name: str) -> Any:
+    if name == "validation":
+        import warnings
+        import pystac.validation
+
+        warnings.warn(
+            "pystac.validation will not be automatically imported to the package in "
+            "pystac v2.0. Instead, import it directly: `import pystac.validation`",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return pystac.validation
+    raise AttributeError(f"module '{__name__}' has no attribute '{name}'")