code: def bbox(self):
          
          xmin = min(self.start.real, self.end.real)
          xmax = max(self.start.real, self.end.real)
          ymin = min(self.start.imag, self.end.imag)
          ymax = max(self.start.imag, self.end.imag)
          return xmin, xmax, ymin, ymax
docs: returns the bounding box for the segment in the form
          (xmin, xmax, ymin, ymax).