Schema docs, "modulu a record's 'id' key'" ?

[velle]

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From Keeping Schemas Simple

Fiona takes a less is more approach to record types and schemas. Data about record types is structured as closely to data about records as can be done. Modulo a record’s ‘id’ key, the keys of a schema mapping are the same as the keys of the collection’s record mappings.

I know what modulo is in terms of math. But despite reading this paragraph several times, I can't figure out what the meaning is here.

[sgillies]

@velle I mean "except for the record's id key". I should just say that instead.