code: function filter(filterName, pattern, options) {
      return function() {
        options = options || {};
        filters[filterName] = gFilter(pattern, options);
        return filters[filterName];
      };
    }
docs: Creates a filter function that filters a vinyl stream when invoked. Additionally stores the filter in memory
  for use with filter.restore.
  
  @name filter
  @param {string} filterName - The name of the filter to create. Should be namespaced to avoid collisions.
  @param {*} pattern - The source glob pattern(s) to filter the vinyl stream.
  @param {object} [options] - The additional options to pass to gulp-filter.
  @returns {function} - The partial that generates the vinyl filter when invoked.
  @see https://github.com/sindresorhus/gulp-filter