code: func MustNewPairList(permissiblePairs map[string][]string, defaults map[string]string) *PairList {
  	pl, err := NewPairList(permissiblePairs, defaults)
  	if err != nil {
  		panic(err)
  	}
  	return pl
  }
docs: // MustNewPairList is the same as NewPairList, but panics instead of returning error
  // So check that your defaults are correct :-)