[BUG] AssertionError when running ifpd2 query

[wenjingk]

ifpd2 query --region 101610835 101640700 -N 96 -M 1 -D 2 -w 0.01 \
            --single db/db.oligo_windows/ chrX probe_test7

[01/27/22 14:41:19] INFO     Log to: 'probe_test7/ifpd2-main.log'                                                                               logging.py:22
                    INFO     * OligoProbeBuilder *                                                                                               query.py:216
                             Aim to build probes with 96 oligos each.
                             Off-target threshold range set at (0, 99).
                             Threshold on the delta free energy of the most stable secondary structure
                             set at range [0.0, 50.0]% of the delta free energy of hybridization.
                             Melting temperature range of 20.0 degC.
                             Minimum distance between consecutive oligos in a probe set at 2 nt.
                             Probe size threshold set at 10000 nt.
                             Reducing probes when oligo intersection fraction is equal to or greater than 0.5.
                    INFO     * Walker *                                                                                                         walker.py:361
                             Threads: 1
                             Database: 'db/db.oligo_windows/'
                             Region of interest: chrX:101610835-101640700
                             Aim to scout 1 windows.
                             Using a central focus region of 8000 nt, in windows of size 29865 nt,
                             built with a shift of 29865.0 nt (100.0%).
                             Thus, a total of 1 window sets will be explored.
                    INFO     Prepared a pool of 1 threads.                                                                                      walker.py:465
Parsing records:  49%|██████████████████████████████████████████████▌                                                | 29393/60019 [00:06<00:06, 4923.16it/s][01/27/22 14:41:25] INFO     Reached destination                                                                                                walker.py:414
                    INFO     Parsed 29805/29805 records.                                                                                        walker.py:486
[01/27/22 14:41:27] INFO     Window 0.0 sent to pool.                                                                                           walker.py:576
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 577, in process_window_async
    results = Walker.process_window(
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 625, in process_window
    results = fprocess(oGroup, window, *args, **kwargs)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 657, in fprocess
    probe_list = opb.start(oGroup, window, kwargs["cfr_step"], logger)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/probe.py", line 382, in start
    return self.__build_probe_candidates(oGroup, window, cfr_step, logger)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/probe.py", line 402, in __build_probe_candidates
    if not oGroup.expand_focus_by_step(cfr_step):
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/oligo.py", line 254, in expand_focus_by_step
    raise AssertionError
AssertionError
"""
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/home/unknown/.local/bin/ifpd2", line 8, in <module>
    sys.exit(main())
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/click/core.py", line 1659, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/scripts/query.py", line 234, in main
    ow.start(
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 339, in start
    self.__start_walk(
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 488, in __start_walk
    self.__end_walk(parsing_output)
  File "/home/unknown/.local/pipx/venvs/ifpd2/lib/python3.8/site-packages/ifpd2/walker.py", line 455, in __end_walk
    s, w, results = promise.get()
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 771, in get
    raise self._value
AssertionError