tml_is_action()

function tml_is_action( $action = '' ) {
    $is_action      = false;
    $current_action = tml_get_action();

    if ( $current_action && array_key_exists( $current_action->get_name(), tml_get_actions() ) ) {
        if ( empty( $action ) ) {
            $is_action = true;
        } elseif ( $action === $current_action->get_name() ) {
            $is_action = true;
        }
    }

    /**
     * Filter whether a TML action is being requested or not.
     *
     * @since 7.0
     *
     * @param bool   $is_action Whether a TML action is being requested or not.
     * @param string $action    The action name.
     */
    return apply_filters( 'tml_is_action', $is_action, $action );
}

View src/includes/actions.php, line 216 on GitHub