Make Units.waveform_unit configurable

[rly]

Fixes #2162.

Updates the nwb-schema submodule to the latest schema dev (2.10.1-alpha), which includes NeurodataWithoutBorders/nwb-schema#707 and NeurodataWithoutBorders/nwb-schema#709.

Configurable waveform unit (nwb-schema#707)

That PR changes the unit attribute of Units.waveform_mean, waveform_sd, and waveforms from a fixed value of "volts" to a default value of "volts".

HDMF short-circuits attribute resolution when a spec has a fixed value, so the existing mapping from Units.waveform_unit onto the unit attribute was never reached. With the schema change it is reachable, so no write-path change was needed.

Also implements the warning placeholder in UnitsMap._get_waveform_stat, since a file can now carry different unit values across the three waveform columns while the Units container holds only one.

Waveform peak alignment (nwb-schema#709)

That PR adds an optional time_before_peak_in_ms attribute to Units.waveform_mean, waveform_sd, and waveforms. It holds the time, in milliseconds, from the start of each waveform to the spike peak, that is, the alignment point used during spike sorting. The value is the same for every unit and every spike.

PyNWB exposes it as the waveform_time_before_peak_in_ms constructor argument and field of Units, following the existing waveform_rate and waveform_unit pattern: one value on the container, written onto all three waveform columns, and read back from the first populated column with a warning when the columns disagree.

NO_OVERRIDE in UnitsMap

The constructor argument overrides in UnitsMap returned None to signal "no override". HDMF 6.2.0 deprecates that in favor of the ObjectMapper.NO_OVERRIDE sentinel, and under HDMF 8.0 a None return will set the constructor argument to None, which would clobber the "volts" default of waveform_unit. They now return the sentinel via the existing pynwb.io.utils.NO_OVERRIDE shim.

Note

waveform_unit, waveform_rate, and waveform_time_before_peak_in_ms can only be set on the Units constructor, so they are not reachable from the nwbfile.add_unit(...) path that auto-creates the table. Worth addressing separately.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.25%. Comparing base (5101a86) to head (22e6492).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2237      +/-   ##
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+ Coverage   96.04%   96.25%   +0.20%     
==========================================
  Files          30       30              
  Lines        3010     3018       +8     
  Branches      437      438       +1     
==========================================
+ Hits         2891     2905      +14     
+ Misses         67       64       -3     
+ Partials       52       49       -3     

Flag	Coverage Δ
integration	74.71% <100.00%> (+0.26%)	⬆️
unit	86.67% <25.00%> (-0.10%)	⬇️

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[h-mayorquin]

Thanks for this, looks good to me.

[h-mayorquin]

If we are improving the metadata provenance for waveforms it would be great to get this one as well (c.c. @alejoe91)

NeurodataWithoutBorders/nwb-schema#709

[h-mayorquin]

Thanks for moving quickly with this. LGTM.