code: function processFiles(bucket, key, transform, cb, currentFileNum=0, lastFileNum=0, arn=null, retries=0) {
    const maxRetries = 5
  
    var nextFileNum = (currentFileNum < lastFileNum) ? currentFileNum + 1 : null
    //invokeLambda(bucket, key, currentFileNum, lastFileNum, arn)
  
    processFile(
      bucket, `${key}${currentFileNum}.csv`, transform
    ).then((n_scenes) => {
      invokeLambda(bucket, key, nextFileNum, lastFileNum, arn, 0)
      cb()
    }).catch((e) => {
      // if CSV failed, try it again
      if (retries < maxRetries) {
        invokeLambda(bucket, key, currentFileNum, lastFileNum, arn, retries + 1)
      } else {
        // log and move onto the next one
        console.log(`error: maxRetries hit in file ${currentFileNum}`)
        invokeLambda(bucket, key, nextFileNum, lastFileNum, arn, 0)
      }
      cb()
    })
  }
docs: Process 1 or more CSV files by processing one at a time, then invoking the next