Add Catalog.get_collections method

Author: duckontheweb

pystac/catalog.py

@@ -320,6 +320,14 @@ def get_children(self) -> Iterable[Union["Catalog", "Collection_Type"]]:
             self.get_stac_objects(pystac.RelType.CHILD),
         )
 
+    def get_collections(self) -> Iterable["Collection_Type"]:
+        """Return all children of this catalog that are :class:`~pystac.Collection`
+        instances."""
+        return map(
+            lambda x: cast(pystac.Collection, x),
+            self.get_stac_objects(pystac.RelType.CHILD, pystac.Collection),
+        )
+
     def get_child_links(self) -> List[Link]:
         """Return all child links of this catalog.
 

tests/test_catalog.py

@@ -996,6 +996,13 @@ def testfrom_invalid_dict_raises_exception(self) -> None:
         with self.assertRaises(pystac.STACTypeError):
             _ = pystac.Catalog.from_dict(collection_dict)
 
+    def test_get_collections(self) -> None:
+        catalog = TestCases.test_case_2()
+        collections = list(catalog.get_collections())
+
+        self.assertGreater(len(collections), 0)
+        self.assertTrue(all(isinstance(c, pystac.Collection) for c in collections))
+
 
 class FullCopyTest(unittest.TestCase):
     def check_link(self, link: pystac.Link, tag: str) -> None: