attempting to fix mypy in windows CI

Author: tclose

fileformats/generic/fsobject.py

@@ -1,7 +1,6 @@
 import os
-import platform
 import typing as ty
-from pathlib import Path
+from pathlib import Path, WindowsPath
 from fileformats.core.fileset import FileSet
 from fileformats.core.exceptions import (
     FormatMismatchError,
@@ -60,7 +59,7 @@ def exists(self) -> bool:
         return True
 
     def group(self) -> ty.Optional[str]:
-        if platform.system() == "Windows":
+        if isinstance(self.fspath, WindowsPath):
             return None
         return self.fspath.group()
 
@@ -75,7 +74,7 @@ def name(self) -> str:
         return self.fspath.name
 
     def owner(self) -> ty.Optional[str]:
-        if platform.system() == "Windows":
+        if isinstance(self.fspath, WindowsPath):
             return None
         return self.fspath.owner()