code: def masked(self, invmask, replacement=""):
      # type: (Union[np.ndarray, List[int]], str) -> SplitResult
      s = self.copy()
      s.tokens[invmask] = replacement
      return s
  
imports: from __future__ import absolute_import
  import re
  import math
  from typing import List, Tuple, Union, Optional
  import numpy
  from sklearn.utils import check_random_state
  from eli5.utils import indices_to_bool_mask, vstack
label_desc: Use image node_id 7 for calling the SplitResult obj's underlying member method code with example usage: obj.masked(invmask, replacement) and returns: s