docs: public <R> SingleOutputStreamOperator<R> flatSelect(
  			final PatternFlatSelectFunction<T, R> patternFlatSelectFunction,
  			final TypeInformation<R> outTypeInfo) {
  
  		final PatternProcessFunction<T, R> processFunction =
  			fromFlatSelect(builder.clean(patternFlatSelectFunction))
  				.build();
  
  		return process(processFunction, outTypeInfo);
  	}