[Feature]: allow modification of fields of unbound containers

[bendichter]

What would you like to see added to HDMF?

Add field to containers indicating if they are bound to a file or unbound (in memory only)

Is your feature request related to a problem?

The motivation is we would like to set chunking and compression after specifying the data

What solution would you like?

For unbound containers, you should be able to change existing fields

Do you have any interest in helping implement the feature?

No.

Code of Conduct

• [X] I agree to follow this project's Code of Conduct
• [X] Have you checked the Contributing document?
• [X] Have you ensured this change was not already requested?

[rly]

Check container_source

[rly]

See also #411