code: func fillOptions(options *Options) *Options {
  	if options == nil {
  		options = &Options{}
  	}
  
  	if options.Encoder == nil {
  		options.Encoder = DefaultEncode
  	}
  	if options.Decoder == nil {
  		options.Decoder = DefaultDecode
  	}
  
  	return options
  }
docs: // set any unspecified options to defaults