code: def _gripper_visualization(self):
          
  
          # color the gripper site appropriately based on distance to cube
          if self.gripper_visualization:
              # get distance to cube
              cube_site_id = self.sim.model.site_name2id("cube")
              dist = np.sum(
                  np.square(
                      self.sim.data.site_xpos[cube_site_id]
                      - self.sim.data.get_site_xpos("grip_site")
                  )
              )
  
              # set RGBA for the EEF site here
              max_dist = 0.1
              scaled = (1.0 - min(dist / max_dist, 1.)) ** 15
              rgba = np.zeros(4)
              rgba[0] = 1 - scaled
              rgba[1] = scaled
              rgba[3] = 0.5
  
              self.sim.model.site_rgba[self.eef_site_id] = rgba
docs: Do any needed visualization here. Overrides superclass implementations.