_getFilesForInstall(targetFiles) {
    let files = this.files(this.options);

    // if we've defined targetFiles, get file info on ones that match
    return (targetFiles && targetFiles.length > 0 && intersection(files, targetFiles)) || files;
  }
@private
    @method _getFilesForInstall
    @param {Array} targetFiles
    @return {Array} files