Why only "left_gaze_x" and "left_gaze_y" to recover eye trajectory (PsychoPy Tobii Workshop)?

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My question is better described as "What metric (left_eye or right_eye X Y) is used to calculate and record data such as '“ROI.num_looks”, “ROI.timesOn”, “ROI.timesOff” in PsychoPy output.

I dug into the source code and found out they used the average of left and right eyes X and Y, see the comments in source code below

‘’’

    Device.__init__(self, *args, **kwargs['dconfig'])

    # hold last received ioHub eye sample (in ordered array format) from
    # tracker.
    self._latest_sample = EyeTrackerConstants.FUNCTIONALITY_NOT_SUPPORTED

    # holds the last gaze position read from the eye tracker as an x,y tuple. If binocular recording is
    # being performed, this is an average of the left and right gaze
    # position x,y fields.

‘’’

Left eye X Y Z and right eye X Y Z can be unpacked from the binocular recording (stored in h5py files). To recover the ROI measures from those readings that match with PsychoPy output, the average of left eye and right eye coordinates should be used.