public TerminalCommandBuilder <TEntrypoint, TSettings> AddPositional(PositionalDefinition <TSettings> positionalDefinition)
 {
     this.command.AddPositionalFunction(positionalDefinition.ToUntyped());
     return(this);
 }
 public TerminalCommandBuilder <TEntrypoint, TSettings> AddPositional <T>(
     string name,
     bool required,
     Expression <Func <TSettings, T> > property,
     Conversion <T> converter)
 => this.AddPositional(PositionalDefinition <TSettings> .Create(name, required, property, converter));