Remove isinstance check in _ensure_filesystem

Author: fjetter

python/pyarrow/parquet.py

@@ -646,11 +646,9 @@ def open_file(path, meta=None):
 
 
 def _ensure_filesystem(fs):
- if not isinstance(fs, type):
- fs_type = type(fs)
- else:
- fs_type = fs
+ fs_type = type(fs)
 
+ # If the arrow filesystem was subclassed, assume it supports the full interface and return it
  if not issubclass(fs_type, FileSystem):
  for mro in inspect.getmro(fs_type):
  if mro.__name__ is 'S3FileSystem':