Method for extract metada from nwb to make our round trip testing more complete

[h-mayorquin]

Right now, our ecephys tests with data, the ones in test_gin_ecephys mainly compare the traces as written from the recording extractors.

https://github.com/catalystneuro/nwb-conversion-tools/blob/a875b40e15ff34d593eb70ac45a188b46b21c216/tests/test_on_data/test_gin_ecephys.py#L197-L220

Whereas the corresponding tests for sorting extractor mainly compares the output of the sorting object: https://github.com/catalystneuro/nwb-conversion-tools/blob/a875b40e15ff34d593eb70ac45a188b46b21c216/tests/test_on_data/test_gin_ecephys.py#L284-L289

That is, of the components of the nwb_file, our test cover mostly the effects of the recording extractors and sorters ignoring the metadata.

I am wondering on whether it would be a good idea to create a method get_metadata for nwb files so we can also compare the get_metadata method of the interface with the data as it is written in the nwb file.

Does this makes sense? is there some obvious hurdle that I am not seeing or something that I am missing?