code: function (inputStream, outputStream, tempPath, tempPath2, err, callback) {
        async.parallel({
          unlink: function(cb) {
            if (!tempPath) {
              return callback(null);
            }
            removeLocalBlob(tempPath, cb);
          },
  
          unlink2: function(cb) {
            if (!tempPath2) {
              return callback(null);
            }
            removeLocalBlob(tempPath2, cb);
          },
  
          closeReadStream: function(cb) {
            inputStream.destroy();
            cb();
          },
  
          closeWriteStream: function(cb) {
            outputStream.destroy();
            cb();
          }
        }, cleanupError => {
          if (err) {
            return callback(err);
          }
          return callback(cleanupError);
        });
      }
docs: Implementation detail. Used when stream-based copies fail.  Cleans up the streams and temporary files (which can be null), then delivers err to the callback unless something goes wrong in the cleanup itself in which case that error is delivered.