HDF5 file - how to create a file without hierarchy?

Hi!
In PsychoPy, eyetracking data are stored in ‘groups’ of data files (e.g.:
data_collection/events/eyetracker/BinocularEyeSampleEvent
data_collection/events/eyetracker/KeyboardInputEvent
data_collection/events/eyetracker/MouseInputEvent

Is there a possiblity to get a datafile without hierarchy - just where all data are stored (like the output file of Tobii)?
If this is not possible. How can I integrate the 3 data files above in one file?

Thank you very much!
Best, M