Method constructor

tfjs-data/src/iterators/lazy_iterator.ts:700–704

(
      protected upstream: LazyIterator<I>,
      protected transform: (value: I) => O)

class MapIterator<I, O> extends LazyIterator<O> {
  constructor(
      protected upstream: LazyIterator<I>,
      protected transform: (value: I) => O) {
    super();
  }

  summary() {
    return `${this.upstream.summary()} -> Map`;