Setting an error message to a field manually

->steps([
    Step::make('group selection')
        ->schema([
            Select::make('group_id')
                ->required()
                ->options(fn (): array => Group::query()
                    ->pluck('name', 'id')
                    ->toArray()),
        ])
        ->afterValidation(function (Get $get, Set $set): void {
            calculations
            if (some logic) {
                set error message to group_id field
                throw new Halt();
            }
            $set('next step', some stuff);
        })