function Generate(params) {
    Transform.call(this, [], params);
  }
Generates data tuples using a provided generator function.
@constructor
@param {object} params - The parameters for this operator.
@param {function(Parameters): object} params.generator - A tuple generator
  function. This function is given the operator parameters as input.
  Changes to any additional parameters will not trigger re-calculation
  of previously generated tuples. Only future tuples are affected.
@param {number} params.size - The number of tuples to produce.