code: def invert(dict_):
      
      ensure_mapping(dict_)
      return dict_.__class__(izip(itervalues(dict_), iterkeys(dict_)))
docs: Return an inverted dictionary, where former values are keys
      and former keys are values.
  
      .. warning::
  
          If more than one key maps to any given value in input dictionary,
          it is undefined which one will be chosen for the result.
  
      :param dict_: Dictionary to swap keys and values in
      :return: Inverted dictionary