def METHOD_NAME(self):
    # setting data type from peak dtype
    pfields_ = self.deps['peaks'].dtype_for('peaks').fields
    # populating data type
    infoline = {'s1': 'main S1',
                's2': 'main S2',
                'alt_s1': 'alternative S1',
                'alt_s2': 'alternative S2',
               }
    dtype = []
    # populating APC
    ptypes = ['s1', 's2', 'alt_s1', 'alt_s2']
    for type_ in ptypes:
        dtype += [((f'Area per channel for {infoline[type_]}', f'{type_}_area_per_channel'),
                 pfields_['area_per_channel'][0])]
        dtype += [((f'Length of the interval in samples for {infoline[type_]}', f'{type_}_length'),
                 pfields_['length'][0])]
        dtype += [((f'Width of one sample for {infoline[type_]} [ns]', f'{type_}_dt'),
                 pfields_['dt'][0])]
    # populating S1 n channel properties
    n_channel_dtype = [(("Main S1 count of contributing PMTs", "s1_n_channels"),
              np.int16),
             (("Main S1 top count of contributing PMTs", "s1_top_n_channels"),
              np.int16),
             (("Main S1 bottom count of contributing PMTs", "s1_bottom_n_channels"),
              np.int16),
             ]
    return {
        "event_area_per_channel": dtype + n_channel_dtype + strax.time_fields,
        "event_n_channel": n_channel_dtype + strax.time_fields,
    }