code: 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);
  	}
docs: Applies a flat select function to the detected pattern sequence. For each pattern sequence
  the provided {@link PatternFlatSelectFunction} is called. The pattern flat select function
  can produce an arbitrary number of resulting elements.
  
  @param patternFlatSelectFunction The pattern flat select function which is called for each
  detected pattern sequence.
  @param <R> Type of the resulting elements
  @param outTypeInfo Explicit specification of output type.
  @return {@link DataStream} which contains the resulting elements from the pattern flat select
  function.