code: func AddConversionByType(srcType reflect.Type, targetType reflect.Type, converter Converter) {
  	if _, ok := converterMap[srcType]; !ok {
  		converterMap[srcType] = map[reflect.Type]Converter{}
  	}
  	converterMap[srcType][targetType] = converter
  }
docs: // AddConversionByType allows registering a custom `Converter` into golbal `converterMap` by types.