docs: def islink(self, path=None, header=None):
          """
          Returns True if object is a symbolic link.
  
          Args:
              path (str): File path or URL.
              header (dict): Object header.
  
          Returns:
              bool: True if object is Symlink.
          """
          if header is None:
              header = self._head(self.get_client_kwargs(path))
  
          for key in ('x-oss-object-type', 'type'):
              try:
                  return header.pop(key) == 'Symlink'
              except KeyError:
                  continue
          return False