code: public <R> SingleOutputStreamOperator<R> select(
  			final PatternSelectFunction<T, R> patternSelectFunction,
  			final TypeInformation<R> outTypeInfo) {
  
  		final PatternProcessFunction<T, R> processFunction =
  			fromSelect(builder.clean(patternSelectFunction)).build();
  
  		return process(processFunction, outTypeInfo);
  	}
docs: Applies a select function to the detected pattern sequence. For each pattern sequence the
  provided {@link PatternSelectFunction} is called. The pattern select function can produce
  exactly one resulting element.
  
  @param patternSelectFunction The pattern 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 select
  function.