code: def visuals_at(self, pos, radius=10):
          
          tr = self.transforms.get_transform('canvas', 'framebuffer')
          pos = tr.map(pos)[:2]
  
          id = self._render_picking(region=(pos[0]-radius, pos[1]-radius,
                                            radius * 2 + 1, radius * 2 + 1))
          ids = []
          seen = set()
          for i in range(radius):
              subr = id[radius-i:radius+i+1, radius-i:radius+i+1]
              subr_ids = set(list(np.unique(subr)))
              ids.extend(list(subr_ids - seen))
              seen |= subr_ids
          visuals = [VisualNode._visual_ids.get(x, None) for x in ids]
          return [v for v in visuals if v is not None]
docs: Return a list of visuals within *radius* pixels of *pos*.
          
          Visuals are sorted by their proximity to *pos*.
          
          Parameters
          ----------
          pos : tuple
              (x, y) position at which to find visuals.
          radius : int
              Distance away from *pos* to search for visuals.