class_docstr: Container object for the variables defined in a config file.
  
  `VariableSet` can be used as a plain dictionary, with the variable names
  as keys.
  
  Parameters
  ----------
  d : dict
      Dict of items in the "variables" section of the configuration file.
code: def __init__(self, d):
      self._raw_data = dict([(k, v) for k, v in d.items()])
  
      self._re = {}
      self._re_sub = {}
  
      self._init_parse()
  
imports: from __future__ import division, absolute_import, print_function
  import sys
  import re
  import os
label_desc: Use image node_id 1 to create a new VariableSet object from inherited base classes: object with example: obj = VariableSet(d)