How to use the lmdb.InvalidError function in lmdb

def _open_lmbd_readonly(self):
        # We set the mapsize here because LMBD will map 1TB of virtual memory if
        # we don't, making it hard to figure out how much memory we're actually
        # using.
        map_size = None
        try:
            map_size = os.path.getsize(self.path)
        except OSError as e:
            raise exceptions.FileFormatError(str(e)) from e
        try:
            store = zarr.LMDBStore(
                self.path, map_size=map_size, readonly=True, subdir=False, lock=False
            )
        except lmdb.InvalidError as e:
            raise exceptions.FileFormatError(
                "Unknown file format:{}".format(str(e))
            ) from e
        except lmdb.Error as e:
            raise exceptions.FileFormatError(str(e)) from e
        return store