code: function Collector(expected) {
    this.expectKeys = Array.isArray(expected) ? new Set(expected) : null;
    this.expected = this.expectKeys ? expected.length : expected;
    this.keys = new Set();
    this.count = 0;
    this.timer = null;
    this.onDone = common.emptiness;
    this.isDistinct = false;
    this.isDone = false;
    this.data = {};
  }
docs: Data collector expected - <number> | <string[]>, count or keys