code: public ConnectedStreams<IN1, IN2> keyBy(int keyPosition1, int keyPosition2) {
  		return new ConnectedStreams<>(this.environment, inputStream1.keyBy(keyPosition1),
  				inputStream2.keyBy(keyPosition2));
  	}
docs: KeyBy operation for connected data stream. Assigns keys to the elements of
  input1 and input2 according to keyPosition1 and keyPosition2.
  
  @param keyPosition1
  The field used to compute the hashcode of the elements in the
  first input stream.
  @param keyPosition2
  The field used to compute the hashcode of the elements in the
  second input stream.
  @return The grouped {@link ConnectedStreams}