code: def ok_schema_id(token: str) -> bool:
      
  
      return bool(re.match('[{}]{{21,22}}:2:.+:[0-9.]+$'.format(B58), token or ''))
docs: Whether input token looks like a valid schema identifier;
      i.e., <issuer-did>:2:<name>:<version>.
  
      :param token: candidate string
      :return: whether input token looks like a valid schema identifier