UPDATE: #9136 implements this for "raw" ... we still need it for "epochs"

I often find myself doing things like this:

# get EEG data and scale to micro volts
# ntrials x nchannels x ntimes
eeg_data_uV = epochs.get_data() * 1e6

... just to do different kinds of analyses with custom functions.

I think we should add a "unit" parameter to .get_data():

"""
Parameters
----------
unit : str, one of ["nV, uV, mV, V"]
    The unit in which the data will be returned. Defaults to "V".
"""

This would make it more transparent for users what units the data are in they are receiving, and also offer a chance for customization.

I have a complete déjà vu writing up this issue, but I couldn't find existing threads on this.