def make_tetradic_scheme(self, angle=<NUM_LIT:30>, mode='<STR_LIT>'):
h, s, l = self.__hsl<EOL>if mode == '<STR_LIT>': h = rgb_to_ryb(h)<EOL>h1 = (h + <NUM_LIT> - angle) % <NUM_LIT><EOL>h2 = (h + <NUM_LIT>) % <NUM_LIT><EOL>h3 = (h + <NUM_LIT> - angle) % <NUM_LIT><EOL>if mode == '<STR_LIT>':<EOL><INDENT>h1 = ryb_to_rgb(h1)<EOL>h2 = ryb_to_rgb(h2)<EOL>h3 = ryb_to_rgb(h3)<EOL><DEDENT>return (<EOL>Color((h1, s,  l), '<STR_LIT>', self.__a, self.__wref),<EOL>Color((h2, s,  l), '<STR_LIT>', self.__a, self.__wref),<EOL>Color((h3, s,  l), '<STR_LIT>', self.__a, self.__wref))<EOL>
Return three colors froming a tetrad with this one.

        Parameters:
          :angle:
            The angle to substract from the adjacent colors hues [-90...90].
            You can use an angle of zero to generate a square tetrad.
          :mode:
            Select which color wheel to use for the generation (ryb/rgb).

        Returns:
          A tuple of three grapefruit.Color forming a color tetrad with
          this one.

        >>> col = Color.from_hsl(30, 1, 0.5)
        >>> [c.hsl for c in col.make_tetradic_scheme(mode='rgb', angle=30)]
        [(90.0, 1.0, 0.5), (210.0, 1.0, 0.5), (270.0, 1.0, 0.5)]