new_contents: """RGBA Color."""
  from typing import Tuple, Union
  
  from mpf.core.rgb_color import RGBColor
  
  
  class RGBAColor(RGBColor):
  
      """RGB Color with alpha channel."""
  
      def __init__(self, color: Union[RGBColor, Tuple[int, int, int, int]]):
          """Initialise RGBA color."""
          if isinstance(color, RGBColor):
              self.opacity = 255
              super().__init__(color)
          else:
              self.opacity = color[3]
              super().__init__((color[0], color[1], color[2]))
  
      def __iter__(self):
          """Return iterator."""
          return iter([self._color[0], self._color[1], self._color[2], self.opacity])
  
      def __str__(self):
          """Return string representation."""
          return "{} Opacity: {}".format(self._color, self.opacity)
  
subject: implement RGBAColor