SchemeMonochrome constructor 
    
      
      SchemeMonochrome({ - required Hct sourceColorHct, 
- required bool isDark, 
- required double contrastLevel, 
})Implementation
  SchemeMonochrome({
  required Hct sourceColorHct,
  required super.isDark,
  required super.contrastLevel,
}) : super(
        sourceColorArgb: sourceColorHct.toInt(),
        variant: Variant.monochrome,
        primaryPalette: TonalPalette.of(sourceColorHct.hue, 0.0),
        secondaryPalette: TonalPalette.of(sourceColorHct.hue, 0.0),
        tertiaryPalette: TonalPalette.of(sourceColorHct.hue, 0.0),
        neutralPalette: TonalPalette.of(sourceColorHct.hue, 0.0),
        neutralVariantPalette: TonalPalette.of(sourceColorHct.hue, 0.0),
      );