code: def on_draw(self):
          
          # Skip the drawing if the program hasn't been built yet.
          # The program is built by the interact.
          if self.program:
              # Draw the program.
              self.program.draw(self.gl_primitive_type)
          else:  # pragma: no cover
              logger.debug("Skipping drawing visual `%s` because the program "
                           "has not been built yet.", self)
docs: Draw the visual.