code: def selected_mask(self):
      return self._selected_mask
  
imports: import copy
  import logging
  import math
  import random
  import numpy
  import pandas
  from fate.arch import Context
  from ..abc.module import HeteroModule, Module
label_desc: Use image node_id 3 for calling the StandardSelection obj's underlying member method code with example usage: obj.selected_mask() and returns: self