code: function stringify(arc) {
    let fmtTbl = obj=> {
      let name = Object.keys(obj)[0]
      let keys = Object.keys(obj[name])
      let result = `${name}\n`
      keys.forEach(key=> {
        let val = obj[name][key]
        result += `  ${key} ${val}\n`
      })
      return result
    }
    let str = `@app\n${arc.app[0]}\n`
    /////////////////////////////////
    if (arc.http.length > 0)
      str += `\n@http\n` + arc.http.map(tuple=> tuple.join(' ') + '\n').join('')
  
    if (arc.events.length > 0)
      str += `\n@events\n` + arc.events.join('\n') + '\n'
  
    if (arc.queues.length > 0)
      str += `\n@queues\n` + arc.queues.join('\n') + '\n'
  
    if (arc.scheduled.length > 0)
      str += `\n@scheduled\n` + arc.scheduled.map(v=> v.join(' ')).join('\n') + '\n'
  
    if (arc.tables.length > 0)
      str += `\n@tables\n` + arc.tables.map(fmtTbl).join('\n')
  
    if (arc.aws.length > 0)
      str += `\n@aws\n` + arc.aws.map(tuple=> tuple.join(' ') + '\n').join('')
    //////////
    return str
  }
docs: create a .arc string from arc object