code: public <R> SingleOutputStreamOperator<R> map(CoMapFunction<IN1, IN2, R> coMapper) {
  
  		TypeInformation<R> outTypeInfo = TypeExtractor.getBinaryOperatorReturnType(
  			coMapper,
  			CoMapFunction.class,
  			0,
  			1,
  			2,
  			TypeExtractor.NO_INDEX,
  			getType1(),
  			getType2(),
  			Utils.getCallLocationName(),
  			true);
  
  		return transform("Co-Map", outTypeInfo, new CoStreamMap<>(inputStream1.clean(coMapper)));
  
  	}
docs: Applies a CoMap transformation on a {@link ConnectedStreams} and maps
  the output to a common type. The transformation calls a
  {@link CoMapFunction#map1} for each element of the first input and
  {@link CoMapFunction#map2} for each element of the second input. Each
  CoMapFunction call returns exactly one element.
  
  @param coMapper The CoMapFunction used to jointly transform the two input DataStreams
  @return The transformed {@link DataStream}