function Window(params) {
    Transform.call(this, {}, params);
    this._mlen = 0;
    this._mods = [];
  }
Perform window calculations and write results to the input stream.
@constructor
@param {object} params - The parameters for this operator.
@param {function(*,*): number} [params.sort] - A comparator function for sorting tuples within a window.
@param {Array<function(object): *>} [params.groupby] - An array of accessors by which to partition tuples into separate windows.
@param {Array<string>} params.ops - An array of strings indicating window operations to perform.
@param {Array<function(object): *>} [params.fields] - An array of accessors
  for data fields to use as inputs to window operations.
@param {Array<*>} [params.params] - An array of parameter values for window operations.
@param {Array<number>} [params.aggregate_params] - An optional array of parameter values for aggregation operations.
@param {Array<string>} [params.as] - An array of output field names for window operations.
@param {Array<number>} [params.frame] - Window frame definition as two-element array.
@param {boolean} [params.ignorePeers=false] - If true, base window frame boundaries on row
  number alone, ignoring peers with identical sort values. If false (default),
  the window boundaries will be adjusted to include peer values.