def preprocess_data(Xs_raw):
n = len(Xs_raw)<EOL>Xs_raw_mean = sum(X for X in Xs_raw) / n<EOL>return [X - Xs_raw_mean for X in Xs_raw], Xs_raw_mean<EOL>
Translate the center of mass (COM) of the data to the origin.
    Return the prossed data and the shift of the COM