code: def unset(self, point):
          
          if not isinstance(point, Point):
              point = Point(point)
  
          x, y = self.round(point.x) >> 1, self.round(point.y) >> 2
  
          if (x, y) not in self.screen:
              return
  
          if isinstance(self.screen[y][x], int):
              self.screen[(x, y)] &= ~self.pixels[y & 3][x & 1]
  
          else:
              del self.screen[(x, y)]
  
          if not self.screen.canvas.get(y):
              del self.screen[y]
docs: Unset pixel at (x, y) point.