code: function _uploadFile(incomingFd, incomingFileStream, handleProgress, s3ClientOpts, done) {
    // https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#upload-property
    var s3ManagedUpload = _buildS3Client(s3ClientOpts)
    .upload(_stripKeysWithUndefinedValues({
      Bucket: s3ClientOpts.bucket,
      Key: incomingFd.replace(/^\/+/, ''),//« remove any leading slashes
      Body: incomingFileStream,
      ContentType: mime.getType(incomingFd)//« advisory; makes things nicer in the S3 dashboard
    }), (err, rawS3ResponseData)=>{
      if (err) {
        return done(err);
      } else {
        return done(undefined, {
          rawS3ResponseData
        });
      }
    });//_∏_
  
    s3ManagedUpload.on('httpUploadProgress', (event)=>{
      // console.log('upload progress');
      let written = _.isNumber(event.loaded) ? event.loaded : 0;
      let total = _.isNumber(event.total) ? event.total : undefined;
      let handledSuccessfully = handleProgress(_stripKeysWithUndefinedValues({
        name: incomingFileStream.filename || incomingFd,
        fd: incomingFd,
        written,
        total,
        percent: total ? (written / total) : undefined
      }));
      if (!handledSuccessfully) {
        s3ManagedUpload.abort();
      }
    });//œ
  
  }
docs: ƒ