code: def get_dimension(self):
          
          if self.strokes > 0:
              if self.pixel_env > 0:
                  return (2 + (1 + 2*self.pixel_env)**2) \
                      * self.strokes * self.points_per_stroke
              else:
                  return 2*self.strokes * self.points_per_stroke
          else:
              if self.pen_down:
                  return 3*self.points_per_stroke
              else:
                  return 2*self.points_per_stroke
docs: Get the dimension of the returned feature. This equals the number
             of elements in the returned list of numbers.