code: function IteratorOptions(options) {
    this.gte = null;
    this.lte = null;
    this.keys = true;
    this.values = false;
    this.fillCache = false;
    this.keyAsBuffer = true;
    this.valueAsBuffer = true;
    this.reverse = false;
    this.highWaterMark = 16 * 1024;
  
    // Note: do not add this property.
    // this.limit = null;
  
    if (options)
      this.fromOptions(options);
  }
docs: Iterator Options
  @constructor
  @ignore
  @param {Object} options