Describe the new feature or enhancement

In https://mne.tools/stable/generated/mne.time_frequency.EpochsTFR.html#mne.time_frequency.EpochsTFR.average one can currently compute the average of the TFR over all Epochs. This simply calls the numpy.mean function.

Would it be possible to add additional combination possibilities, such as np.median, np.percentile, such that average(func) is now possible, with the list of funcs being possible are numpy functions that operate along the epochs axis.

Describe possible alternatives

One can always compute this themselves, I suppose, but then they lose access to AverageTFR api functionality.