def METHOD_NAME(self, environment, secret_name):
    secret = environment.get_secret(secret_name)
    if not isinstance(secret, list):
        print("Cannot append. '{}' is not a list.".format(secret_name))
        exit(-1)
    value_to_append = getpass.getpass("Value for '{}' to append to '{}': ".format(environment.name, secret_name))
    secret.append(value_to_append)
    environment.secrets_backend.set_secret(secret_name, secret)