Should layout.get_entities return meta-data keys?

[adelavega]

pybids currently returns both entities and meta-data keys (all in dataset) by default.

ancp-bids does not yet support listing all meta-data keys in dataset. presumably this is a useful feature we should implement, but if we do, should this be the default thing that is returned? (presumably it will be somewhat expensive)

[erdalkaraca]

@adelavega great to see that you applied the query language to search for all metadata artifacts, that is exactly how it was expected to be used... in the current implementation of the _get_unique_metadata() only hashable values are added to the final metadata dict, i.e. complex keys will be ignored... is this by purpose?

[adelavega]

Great!

Yes this is on purpose because it returns a list of unique values for each entity, and non-hashables are more difficult to do a "set" on.

This is only a problem for a minority meta-data keys, and a lazy way to temporarily solve this problem, but when we re-design the API, we can think of other ways to handle this.