/// <summary>
    /// Set the <see cref="AsciiDoctorJRunnerSettings.Backend"/> to a builtin backend.
    /// Possible values are <see cref="BuiltinBackend"/>.
    /// For non-builtin backends (i.e. plugins) use <see cref="WithBackend(AsciiDoctorJRunnerSettings, string)"/>.
    /// </summary>
    /// <param name="this">The <see cref="AsciiDoctorJRunnerSettings"/> that extended by this.</param>
    /// <param name="backend">The <see cref="BuiltinBackend"/> to set.</param>
    /// <returns>The reference to the <see cref="AsciiDoctorJRunnerSettings"/>.</returns>
    public static AsciiDoctorJRunnerSettings WithBuiltinBackend(this AsciiDoctorJRunnerSettings @this, BuiltinBackend backend)
    {
        // ReSharper disable PossibleNullReferenceException
        @this.Backend = Enum.GetName(typeof(BuiltinBackend), backend) !.ToLowerInvariant();

        // ReSharper enable PossibleNullReferenceException
        return(@this);
    }
 /// <summary>
 /// Set the <see cref="AsciiDoctorJRunnerSettings.Backend"/> to a builtin backend.
 /// Possible values <seealso cref="BuiltinBackend"/>
 /// </summary>
 /// <param name="this"></param>
 /// <param name="backend"></param>
 /// <returns></returns>
 public static AsciiDoctorJRunnerSettings WithBuiltinBackend(this AsciiDoctorJRunnerSettings @this, BuiltinBackend backend)
 {
     @this.Backend = Enum.GetName(typeof(BuiltinBackend), backend).ToLower(CultureInfo.InvariantCulture);
     return(@this);
 }