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()
Called by FUSE when a file is opened.

        Determines if the provided path and open flags are valid.