code: def _normalizePoint(self, x, y):
          
          # cast to int, always faster than type checking
          x = int(x)
          y = int(y)
  
          assert (-self.width <= x < self.width) and \
                 (-self.height <= y < self.height), \
                 ('(%i, %i) is an invalid postition on %s' % (x, y, self))
  
          # handle negative indexes
          return (x % self.width, y % self.height)
docs: Check if a point is in bounds and make minor adjustments.
  
          Respects Pythons negative indexes.  -1 starts at the bottom right.
          Replaces the _drawable function