Set

to be used as a return object of dynamodb getItem
@constructor
function Set(iter, options) {
  if (!(this instanceof Set)) return new Set(iter, options);

  this._o = {};
  this.length = 0;

  // parse options
  if (options) {
    this.byValue = options.byValue || false; // for objects to use values instead of keys
  }

  // construct set
  if (iter) {
    if ( iter.constructor === Array) {
      this._arr_construct(iter)
    } else if (iter.constructor === Object) {
      this._obj_construct(iter);
    } else {
      throw new errors.InvalidParametersError("Invalid Object");
    }
  }
}