TSV lookup tables for segmentation do not allow extra columns

[Remi-Gau]

See here:

https://bids-specification.readthedocs.io/en/latest/derivatives/imaging.html#common-image-derived-labels

bids-specification/src/schema/rules/tabular_data/derivatives/common_derivatives.yaml

Line 2 in 6a40161

SegmentationLookup:

Is there a reason for this?

For context I am trying to use this to help standardize the atlases in nilearn and adding some extra columns would be handy.

[Remi-Gau]

@effigies forgot to ask you about this one yesterday?

[effigies]

I doubt it:

bids-specification/src/schema/rules/tabular_data/derivatives/common_derivatives.yaml

Lines 2 to 13 in 00917e6

	SegmentationLookup:
	selectors:
	- dataset.dataset_description.DatasetType == "derivative"
	- intersects([suffix], ["dseg", "probseg"])
	columns:
	index: required
	name__segmentations: required
	abbreviation: optional
	color: optional
	mapping: optional
	index_columns: [index]

We have no additional_columns field, so it's presumably defaulting to not allowed. IMO we should probably default to allowed, and in any event I don't see any reason not to allow (or at least "allowed_if_defined") this one.

cc @rwblair for thoughts.