def find_key_by_subkey(self, subkey):
        """Find a key by a fingerprint of one of its subkeys.

        :param str subkey: The fingerprint of the subkey to search for.
        """
        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)
Find a key by a fingerprint of one of its subkeys.

        :param str subkey: The fingerprint of the subkey to search for.