Perserve class in Collection.clone

Author: duckontheweb

pystac/collection.py

@@ -638,7 +638,8 @@ def to_dict(self, include_self_link: bool = True) -> Dict[str, Any]:
         return d
 
     def clone(self) -> "Collection":
-        clone = Collection(
+        cls = self.__class__
+        clone = cls(
             id=self.id,
             description=self.description,
             extent=self.extent.clone(),

tests/test_collection.py

@@ -388,3 +388,9 @@ def test_from_file_returns_subclass(self) -> None:
         custom_collection = self.BasicCustomCollection.from_file(self.MULTI_EXTENT)
 
         self.assertIsInstance(custom_collection, self.BasicCustomCollection)
+
+    def test_clone(self) -> None:
+        custom_collection = self.BasicCustomCollection.from_file(self.MULTI_EXTENT)
+        cloned_collection = custom_collection.clone()
+
+        self.assertIsInstance(cloned_collection, self.BasicCustomCollection)