'Aux Function: detrend, baseline correct, offset, decim.
Note: operates inplace'

@verbose
def _detrend_offset_decim(self, epoch, verbose=None):

    if ((epoch is None) or isinstance(epoch, string_types)):
        return epoch
    if (self.detrend is not None):
        picks = _pick_data_channels(self.info, exclude=[])
        epoch[picks] = detrend(epoch[picks], self.detrend, axis=1)
    picks = pick_types(self.info, meg=True, eeg=True, stim=False, ref_meg=True, eog=True, ecg=True, seeg=True, emg=True, bio=True, ecog=True, fnirs=True, exclude=[])
    epoch[picks] = rescale(epoch[picks], self._raw_times, self.baseline, copy=False, verbose=False)
    if (self._offset is not None):
        epoch += self._offset
    epoch = epoch[:, self._decim_slice]
    return epoch
