code: def _empty_region(self):
      return None
  
imports: import sys
  import numpy
  import pandas
  from ..core import Dataset, NdOverlay, util
  from ..streams import Lasso, Selection1D, SelectionXY
  from ..util.transform import dim
  from .annotation import HSpan, VSpan
label_desc: Use image node_id 2 for calling the SelectionIndexExpr obj's underlying member method code with example usage: obj._empty_region() and returns: None