code: def find_key_by_subkey(self, subkey):
          
          for key in self.list_keys():
              for sub in key['subkeys']:
                  if sub[0] == subkey:
                      return key
          raise LookupError(
              "GnuPG public key for subkey %s not found!" % subkey)
docs: Find a key by a fingerprint of one of its subkeys.
  
          :param str subkey: The fingerprint of the subkey to search for.