docs: def logical_size(self, name):
          """Returns the logical size (before compression) of file `name`."""
          digest = self._digest_for_link(name)
          logical_size = self.db.get('{}:logical_size'.format(digest).encode())
  
          if logical_size:
              return int(logical_size.decode())
          else:
              raise RuntimeError(
                      'Blob doesn\'t have :logical_size in DB: try recovering')