docs: def normalized_rgb(self):
          r"""
          Returns a tuples of the normalized values of the red, green, and blue
          channels of the Colour.
  
          Returns:
              tuple: the rgb values of the colour (with values normalized between
                     0.0 and 1.0)
  
          .. note::
  
              Uses the formula:
  
              \\[ r_{norm} = \\begin{cases}
              \\frac{r_{255}}{12.92}\\ \\qquad &\\text{if $r_{255}$ $\\le$ 0.03928}
              \\\\
              \\left(\\frac{r_{255} + 0.055}{1.055}\\right)^{2.4}
              \\quad &\\text{otherwise}
              \\end{cases} \\]
  
          `Source <http://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef>`_
          """
  
          r1 = self._r / 255
          g1 = self._g / 255
          b1 = self._b / 255
  
          if r1 <= 0.03928:
              r2 = r1 / 12.92
          else:
              r2 = math.pow(((r1 + 0.055) / 1.055), 2.4)
          if g1 <= 0.03928:
              g2 = g1 / 12.92
          else:
              g2 = math.pow(((g1 + 0.055) / 1.055), 2.4)
          if b1 <= 0.03928:
              b2 = b1 / 12.92
          else:
              b2 = math.pow(((b1 + 0.055) / 1.055), 2.4)
  
          return (r2, g2, b2)