def draw_head_none(context):
    """
    Draw an 'x' on the line end to indicate no navigability at
    association head.
    """
    cr = context.cairo
    cr.move_to(6, -4)
    cr.rel_line_to(8, 8)
    cr.rel_move_to(0, -8)
    cr.rel_line_to(-8, 8)
    cr.stroke()
    cr.move_to(0, 0)
