code: def tree_encoder(self):
      # breadth first tree traverse to encode nodes
      # root is encoded as '#', a subnode of root is '#01' if code_length is 2
      # then a 3rd level node is '#01#01'
      # we can use string to encode tree strcuture for those trees without multiple inherences.
      id2code = {}
      id2code[self._root] = "root"
      children_lengths = map(
          lambda x: len(self._hyponyms[x]), self._hyponyms.keys()
      )
      n = max(children_lengths)
      code_length = 1
      for i in range(1, 8):
          if i * 10 - n > 0:
              break
          code_length = i
      coder = lambda x: "#%0*d" % (code_length, x)
      queue = deque([self._root])
      while queue:
          node = queue.popleft()
          if node in self._hyponyms:
              node_code = id2code[node]
              hypos = self._hyponyms[node]
              for i, child in enumerate(hypos):
                  queue.append(child)
                  id2code[child] = node_code + coder(i)
      return id2code
  
imports: from abc import ABCMeta, abstractmethod
  from collections import deque
  from itertools import combinations
  import networkx
  import numpy
  from sematch.semantic.ontology import DBpedia
  from sematch.utility import FileIO
  from sematch.semantic.sparql import StatSPARQL
  import math
label_desc: Use image node_id 2 for calling the Taxonomy obj's underlying member method code with example usage: obj.tree_encoder() and returns: id2code