function Values$1(params) {
    Transform.call(this, null, params);
  }
Extracts an array of values. Assumes the source data has already been
reduced as needed (e.g., by an upstream Aggregate transform).
@constructor
@param {object} params - The parameters for this operator.
@param {function(object): *} params.field - The domain field to extract.
@param {function(*,*): number} [params.sort] - An optional
  comparator function for sorting the values. The comparator will be
  applied to backing tuples prior to value extraction.