code: def __setitem__(self, index, value):
      raise ValueError("%s may not be modified" % type(self).__name__)
  
imports: from nltk.probability import ProbabilisticMixIn
  from nltk.tree.parented import MultiParentedTree, ParentedTree
  from nltk.tree.tree import Tree
label_desc: Use image node_id 2 for calling the ImmutableTree obj's underlying member method code with example usage: obj.__setitem__(index, value) without return types