code: def __str__(self):
      return "*".join("%s" % p for p in self.pieces)
  
imports: import re
  from functools import total_ordering
  from xml.etree import ElementTree
  from nltk.corpus.reader.api import *
  from nltk.corpus.reader.util import *
  from nltk.internals import raise_unorderable_types
  from nltk.tree import Tree
label_desc: Use image node_id 2 for calling the PropbankChainTreePointer obj's underlying member method code with example usage: obj.__str__() and returns: str