vendors/tempy.js/pipe
    function merge2() {
      const streamsQueue = [];
      const args = slice.call(arguments);
      let merging = false;
      let options = args[args.length - 1];
      if (options && !Array.isArray(options) && options.pipe == null) {
        args.pop();
      } else {
        options = {};
      }
      const doEnd = options.end !== false;
      const doPipeError = options.pipeError === true;
      if (options.objectMode == null) {
        options.objectMode = true;
      }
      if (options.highWaterMark == null) {
        options.highWaterMark = 64 * 1024;
      }
      const mergedStream = PassThrough(options);
      function addStream() {
        for (let i = 0, len = arguments.length; i < len; i++) {
          streamsQueue.push(pauseStreams(arguments[i], options));
        }
        mergeStream();
        return this;
      }
      function mergeStream() {
        if (merging) {
          return;
        }
        merging = true;
        let streams = streamsQueue.shift();
        if (!streams) {
          process.nextTick(endStream);
          return;
        }
        if (!Array.isArray(streams)) {
          streams = [streams];
        }
        let pipesCount = streams.length + 1;
        function next() {
          if (--pipesCount > 0) {
            return;
          }
          merging = false;
          mergeStream();
        }
        function pipe(stream2) {
          function onend() {
            stream2.removeListener("merge2UnpipeEnd", onend);
            stream2.removeListener("end", onend);
            if (doPipeError) {
              stream2.removeListener("error", onerror);
            }
            next();
          }
          function onerror(err) {
            mergedStream.emit("error", err);
          }
          if (stream2._readableState.endEmitted) {
            return next();
          }
          stream2.on("merge2UnpipeEnd", onend);
          stream2.on("end", onend);
          if (doPipeError) {
            stream2.on("error", onerror);
          }
          stream2.pipe(mergedStream, { end: false });
          stream2.resume();
        }
        for (let i = 0; i < streams.length; i++) {
          pipe(streams[i]);
        }
        next();
      }
      function endStream() {
        merging = false;
        mergedStream.emit("queueDrain");
        if (doEnd) {
          mergedStream.end();
        }
      }
      mergedStream.setMaxListeners(0);
      mergedStream.add = addStream;
      mergedStream.on("unpipe", function(stream2) {
        stream2.emit("merge2UnpipeEnd");
      });
      if (args.length) {
        addStream.apply(null, args);
      }
      return mergedStream;
    }