def split_epochs(epochs):
    """Savely split up one epochs file into two with adequate channel names."""

    epochs_1 = epochs.copy().pick_channels([ch for ch in epochs.ch_names if ch[:4] == "sub1"],
                                           ordered=True)
    epochs_2 = epochs.copy().pick_channels([ch for ch in epochs.ch_names if ch[:4] == "sub2"],
                                           ordered=True)
    
    # rename the channels
    short_ch_map = {ch: ch[5:] for ch in epochs.ch_names}
    epochs_1.rename_channels({key:val for key, val in short_ch_map.items() if key[:4] == "sub1"})
    epochs_2.rename_channels({key:val for key, val in short_ch_map.items() if key[:4] == "sub2"})

    return epochs_1, epochs_2