docs: def open(self, path, flags):
          """Called by FUSE when a file is opened.
  
          Determines if the provided path and open flags are valid.
  
          """
          log.debug('open(): {}'.format(path))
          # ONEDrive is currently read only. Anything but read access is denied.
          if (flags & self._READ_ONLY_ACCESS_MODE) != os.O_RDONLY:
              self._raise_error_permission_denied(path)
          # Any file in the filesystem can be opened.
          attribute = self._get_attributes_through_cache(path)
          return attribute.is_dir()