code: function delimited(item, separator) {
      const definition = new RepetitionWithSeparator({
          definition: toDefinition(item),
          separator: separator
      })
  
      const orgTextParts = _.map([item, separator], toOriginalText)
      definition.orgText = `delimited(${orgTextParts.join(", ")})`
  
      return {
          toRule: toRule,
          definition: definition
      }
  }
docs: rule: A (, B)*