Fix bug with set operations

Author: Bruno Grande

src/dcqc/file.py

@@ -61,7 +61,6 @@ class File(SerializableMixin):
     url: str
     metadata: dict[str, Any]
     type: str
-    _fs: Optional[FS]
 
     LOCAL_REGEX = re.compile(r"((file|osfs)://)?/?[^:]+")
 
@@ -82,6 +81,7 @@ def __init__(
         self.metadata = dict(metadata)
         self.type = self._pop_file_type()
         self.file_name = self._get_file_name()
+        self._fs: Optional[FS]
         self._fs = None
 
     @property

src/dcqc/filesystems/remote_file.py

@@ -4,16 +4,20 @@
 import os
 from array import array
 from collections.abc import Callable, Iterable
-from ctypes import _CData
 from mmap import mmap
 from pickle import PickleBuffer
-from typing import IO, Any, BinaryIO, Optional, Union
+from typing import IO, TYPE_CHECKING, Any, BinaryIO, Optional, Union
 
 from fs.mode import Mode
 
-LinesType = Iterable[
-    Union[bytes, Union[bytearray, memoryview, array[Any], mmap, _CData, PickleBuffer]]
-]
+if TYPE_CHECKING:
+    from ctypes import _CData
+
+    LinesType = Iterable[
+        Union[
+            bytes, Union[bytearray, memoryview, array[Any], mmap, _CData, PickleBuffer]
+        ]
+    ]
 
 
 class RemoteFile(io.IOBase, BinaryIO):

src/dcqc/suites/suite_abc.py

@@ -70,10 +70,10 @@ def list_test_classes(cls) -> tuple[Type[TestABC], ...]:
         for cls in reversed(superclasses):  # Start from the base class
             if hasattr(cls, "add_tests"):
                 add_tests = set(cls.add_tests)  # type: ignore
-                all_tests.union(add_tests)
+                all_tests |= add_tests
             if hasattr(cls, "del_tests"):
                 del_tests = set(cls.del_tests)  # type: ignore
-                all_tests.difference(del_tests)
+                all_tests -= del_tests
 
         return tuple(all_tests)