code: def _keep_one(cur_mask, prev_mask=None, select_col=None):
      if sum(cur_mask) > 0:
          return cur_mask
      else:
          if prev_mask is not None:
              idx = random.choice(prev_mask[prev_mask].index)
          elif select_col is not None:
              idx = random.choice(select_col)
          else:
              idx = random.choice(cur_mask.index)
          cur_mask[idx] = True
  
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 8 for calling the StandardSelection obj's underlying member method code with example usage: obj._keep_one(cur_mask, prev_mask, select_col) and returns: cur_mask