def ellipse_mode(mode='CENTER'):
    """Change the ellipse and circle drawing mode for the p5.renderer.

    :param mode: The new mode for drawing ellipses. Should be one of
        {'CORNER', 'CORNERS', 'CENTER', 'RADIUS'}. This defaults to
        'CENTER' so calling ellipse_mode without parameters will reset
        the sketch's ellipse mode.
    :type mode: str

    """
    global _ellipse_mode
    _ellipse_mode = mode
