gulpfile.js
function css(files, output, options) {
  options = Object.assign({
    banner: false
  }, options);

  return () => {
    var build = gulp.src(files)

    if (options.banner)
      build = build.pipe($.header(banner, {pkg}));

    build = build
      .pipe($.rename('d3.compose.css'))
      .pipe(gulp.dest(output));

    return build;
  };
}
function css(files, output, options) {
  options = Object.assign({
    banner: false
  }, options);

  return () => {
    var build = gulp.src(files)

    if (options.banner)
      build = build.pipe($.header(banner, {pkg}));

    build = build
      .pipe($.rename('d3.compose.css'))
      .pipe(gulp.dest(output));

    return build;
  };
}
Create css build function

@method css
@param {String|Array} files glob
@param {String} output folder
@param {Object} [options]
@param {Boolean} [options.banner = false] Include banner with build
@return {Function}