feat(FCL-532): add ability to retrieve identifiers by type

This is needed to test for the existence of an FCLID before assigning a new one.

src/caselawclient/models/identifiers/__init__.py

@@ -127,6 +127,11 @@ def __delitem__(self, key: Union[Identifier, str]) -> None:
         else:
             super().__delitem__(key)
 
+    def of_type(self, identifier_type: type[Identifier]) -> list[Identifier]:
+        """Return a list of all identifiers of a given type."""
+        uuids = self.keys()
+        return [self[uuid] for uuid in list(uuids) if isinstance(self[uuid], identifier_type)]
+
     def delete_type(self, deleted_identifier_type: type[Identifier]) -> None:
         "For when we want an identifier to be the only valid identifier of that type, delete the others first"
         uuids = self.keys()

tests/models/identifiers/test_identifiers.py

@@ -105,6 +105,12 @@ def test_contains(self, identifiers):
         assert not identifiers.contains(TestIdentifier(value="TEST-333"))
         assert not identifiers.contains(NeutralCitationNumber(value="TEST-111"))
 
+    def test_of_type(self, mixed_identifiers):
+        only_ncns = mixed_identifiers.of_type(NeutralCitationNumber)
+        assert "TEST-999" not in str(only_ncns)
+        assert "[1701] UKSC 999" in str(only_ncns)
+        assert "[1234] UKSC 999" in str(only_ncns)
+
     def test_delete_type(self, mixed_identifiers):
         mixed_identifiers.delete_type(NeutralCitationNumber)
         assert "TEST-999" in str(mixed_identifiers)