code: def rev_reg_id(cd_id: str, tag: str) -> str:
      
  
      return '{}:4:{}:CL_ACCUM:{}'.format(cd_id.split(':', 1)[0], cd_id, tag)
docs: Given a credential definition identifier and a tag, return the corresponding
      revocation registry identifier, repeating the issuer DID from the
      input identifier.
  
      :param cd_id: credential definition identifier
      :param tag: tag to use
      :return: revocation registry identifier