code: def _push_history(self, key, value):
      if self.root:
          hist = self.history.get(key)
          if hist is None:
              hist = self.history[key] = []
          hist.append(value)
  
imports: from collections import OrderedDict
  from pyparsing import lineno
  from pyparsing import col
  import re
  import copy
  from .exceptions import ConfigException, ConfigWrongTypeException, ConfigMissingException
label_desc: Use image node_id 4 for calling the ConfigTree obj's underlying member method code with example usage: obj._push_history(key, value) without return types