code: def _get_picking_ids(self):
      if self._visual._data is None:
          n_markers = 0
      else:
          n_markers = len(self._visual._data["a_position"])
  
      # we only care about the number of markers changing
      if self._n_primitives == n_markers:
          return
      self._n_primitives = n_markers
  
      return np.arange(1, n_markers + 1, dtype=np.uint32)
  
imports: import numpy
  from vispy.visuals.filters import PrimitivePickingFilter
label_desc: Use image node_id 1 for calling the MarkerPickingFilter obj's underlying member method code with example usage: obj._get_picking_ids() and returns: np