code: def _get_diff(environ, label, pop=False):
      
      if pop:
          blob = environ.pop(_variable_name(label), None)
      else:
          blob = environ.get(_variable_name(label))
  
      return _loads(blob) if blob else {}
docs: Get previously frozen key-value pairs.
  
      :param str label: The name for the frozen environment.
      :param bool pop: Destroy the freeze after use; only allow application once.
      :returns: ``dict`` of frozen values.