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_parse_var(self, name, value):
      self._re[name] = re.compile(r"\$\{%s\}" % name)
      self._re_sub[name] = value
  
imports: from __future__ import division, absolute_import, print_function
  import sys
  import re
  import os
label_desc: Use image node_id 3 for calling the VariableSet obj's underlying member method code with example usage: obj._init_parse_var(name, value) without return types