code: function iteratePipeFile () {
      if (!isIterating()) { return undefined; }
  
      let data = iterateData;
      let file = data.collection[data.i];
  
      data.i++;
  
      if (data.i >= data.collection.length) {
          resetIterateData();
          pipeLastFile(file);
      } else {
          pipeFile(file, iteratePipeFile);
      }
  }
docs: Recursively pipe all files.
  
  @function iteratePipeFile
  @api private