Allow easy serialization of the object mne info

[bruAristimunha]

Hey!

MNE.Info is an import object for raw objects, and according to the documentation, it is like an dictionary.

This attribute has a series of governance structures to ensure that we follow some standardization, which is great!

Even though it behaves like a dictionary, it's not exactly a dictionary. The only official way to save is by using .fiff, that this limits the transfer of that file into hub of file, such as hugging face. Ideally, we would save this as a JSON file/yaml file.

I have a question/proposal. Is there a simple way to serialize the MNE info object without individually selecting each field within the object? (This creates a lot of code re-built into each exact field.)

If it doesn't exist, does it make sense to make MNE info more serializable?

[welcome]

Hello! 👋 Thanks for opening your first issue here! ❤️ We will try to get back to you soon. 🚴

[agramfort]

the info structure in mne can contain numpy arrays (e.g. compensation matrices for MEG). Saving this to JSON may therefore not be ideal... but doable... we could have an mne.Info.to_dict and mne.Info.from_dict that attempts to export/import using only types from the standard library. Then the output would be usable by json.dump my 2c

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[bruAristimunha]

Nice, my diagnosis was correct! thank you for the cents @agramfort!

If the rest of the team agrees, I can proceed with the PR.

[bruAristimunha]

@larsoner , @drammock , @sappelhoff , what do you think?

[sappelhoff]

I am all for using standard file formats over FIFF (or even "modded FIFF" which is I think what we often use in mne), whenever possible. Maybe json-ticks can help with the numpy to JSON formatting: https://pypi.org/project/json-tricks/

Having said that, I personally do not have a concrete use case for this right now.

[drammock]

I would do this by defining Info.__getstate__ and Info.__setstate__. No objection in principle. See first if you can do it without adding dependency on jsontricks