code: def visual_at(self, pos):
          
          tr = self.transforms.get_transform('canvas', 'framebuffer')
          fbpos = tr.map(pos)[:2]
  
          try:
              id_ = self._render_picking(region=(fbpos[0], fbpos[1],
                                                 1, 1))
              vis = VisualNode._visual_ids.get(id_[0, 0], None)
          except RuntimeError:
              # Don't have read_pixels() support for IPython. Fall back to
              # bounds checking.
              return self._visual_bounds_at(pos)
          return vis
docs: Return the visual at a given position
  
          Parameters
          ----------
          pos : tuple
              The position in logical coordinates to query.
  
          Returns
          -------
          visual : instance of Visual | None
              The visual at the position, if it exists.