code: def _draw_frozen_pattern(self):
          
  
          self.context.save()
  
          x, y, w, h = self.rect
          self.context.set_source_rgb(0, 0, 1)
          self.context.set_line_width(0.25)
          self.context.rectangle(*self.rect)
          self.context.clip()
  
          for __x in numpy.arange(x-h, x+w, 5):
              self.context.move_to(__x, y + h)
              self.context.line_to(__x + h, y)
          self.context.stroke()
  
          self.context.restore()
docs: Draws frozen pattern, i.e. diagonal lines