audinterface.Segment reorders ends entries when file argument given to process_signal

[hagenw]

import audinterface
import numpy as np

segment = audinterface.Segment(
    process_func=lambda x, sr: audinterface.utils.signal_index([0, 1], [3, 2])
)
signal = np.zeros((1, 3 * 8000))
sampling_rate = 8000

Then we get correctly:

>>> segment.process_signal(signal, sampling_rate)
MultiIndex([('0 days 00:00:00', '0 days 00:00:03'),
            ('0 days 00:00:01', '0 days 00:00:02')],
           names=['start', 'end'])

But when providing the file argument, end times are reordered (maybe sorted?):

>>> segment.process_signal(signal, sampling_rate, file='f')
MultiIndex([('f', '0 days 00:00:00', '0 days 00:00:02'),
            ('f', '0 days 00:00:01', '0 days 00:00:03')],
           names=['file', 'start', 'end'])