code: static <IN, OUT> FlatSelectBuilder<IN, OUT> fromFlatSelect(final PatternFlatSelectFunction<IN, OUT> function) {
  		return new FlatSelectBuilder<>(function);
  	}
docs: Starts constructing a {@link PatternProcessFunction} from a {@link PatternFlatSelectFunction} that
  emitted elements through {@link org.apache.flink.util.Collector}.