ExtendedPropertyDictionary._on_key_changed breaks pickle compatibility

[bkeryan]

Bug Report

Unpickling an nitypes 1.0.0 DigitalWaveform or DigitalWaveformSignals fails because the unpickled ExtendedPropertyDictionary does not have _on_key_changed set

Repro or Code Sample

New regression tests

Expected Behavior

It works

Current Behavior

AttributeError: 'ExtendedPropertyDictionary' object has no attribute '_on_key_changed'

Possible Solution

Update DigitalWaveform to use hasattr to check whether _on_key_changed is present and initialize it if needed

Context

Reviewing #233

Your Environment

• nitypes version: [releases/1.0] cherry pick: Reverse Indices for Digital Waveform Signals (#222) #233
• Python version: 3.10.11

AB#3623937

[bkeryan]

@mikeprosserni If unpickling a multi-signal DigitalWaveform still fails due to the signal order issue, then perhaps the bar for 1.0.0 compatibility should be unpickling a single-signal DigitalWaveform, since that use case shouldn't be affected by the signal order issue.

[mikeprosserni]

@bkeryan

@mikeprosserni If unpickling a multi-signal DigitalWaveform still fails due to the signal order issue, then perhaps the bar for 1.0.0 compatibility should be unpickling a single-signal DigitalWaveform, since that use case shouldn't be affected by the signal order issue.

The equality method on DigitalWaveformSignal specifically ignores the indices, so it looks like this won't be an issue for the test assertion, even with multi-signal waveforms.

    def __eq__(self, value: object, /) -> bool:
        """Return self==value."""
        if not isinstance(value, self.__class__):
            return NotImplemented
        # Do not compare the index or name.
        return np.array_equal(self.data, value.data)