def paint_cube(self, x, y):
<EOL>color = self.next_color()<EOL>cube_pos = [x, y, x + self.cube_size, y + self.cube_size]<EOL>draw = ImageDraw.Draw(im=self.image)<EOL>draw.rectangle(xy=cube_pos, fill=color)<EOL>
Paints a cube at a certain position a color.

Parameters
----------
x: int
    Horizontal position of the upper left corner of the cube.
y: int
    Vertical position of the upper left corner of the cube.