code: function stream (env) {
      let parseStream = parseFilter(env)
  
      let filter = through.obj((file, enc, cb) => cb(), function (cb) {
        parseStream.promise.then(data => {
          this.push(data)
          cb()
        }, cb)
      })
  
      return pipe(parseStream, filter)
    }
docs: Don't pass files through, but pass final data at the end.
  @return {Stream}