class_docstr: class representing nodes in a prefix tree
code: def __str__(self):
      s = ""
      for k in self.children.keys():
          s += k
      return "isWord: " + str(self.isWord) + "; children: " + s
  
file_path: calamari/calamari_ocr/thirdparty/ctcwordbeamsearch/PrefixTree.py
imports: from __future__ import division
  from __future__ import print_function
label_desc: Use image node_id 2 for calling the Node obj's underlying member method code with example usage: obj.__str__() and returns: unknown