code: function (stream) {
          var self = this;
          stream.on('data', function (chunk) {
              self.push(chunk);
          });
          stream.on('end', function () {
              self.push(null);
          });
          this.readableUnit = stream;
          return this;
      }
docs: Set a readable stream for this unit
  @param {stream.Readable|stream.Duplex|stream.Transform} stream - Use this stream as readable stream
  @returns {Unit}