Confusing behavior when setting a ConfigTree to a dictionary

[zmbc]

Not sure if this is a bug per se, or a design issue, but I was very surprised by the output of this:

from vivarium import ConfigTree

config = ConfigTree()

config.update({'foo': {'bar': 'baz'}}, layer='base')

config.foo = {}

print(config)
print(config.foo)

The line config.foo = {} has no effect. I understand that this is consistent with .update, where dictionaries are used as the data model for nested keys and the update'd tree is merged into the current one, but setting an attribute feels like it should never be a no-op; it should either set something, or error.

[zmbc]

The way __setattr__ behaves with dictionaries overall is a bit surprising, even when not a no-op. for example:

from vivarium import ConfigTree

config = ConfigTree(layers=['super_base', 'base'])

config.update({'foo': {'bar': 'baz', 'bar_2': 'baz_2'}}, layer='super_base')

config.foo = {'bar': 'quux'}

print(config)
print(config.foo)

The fact that config.foo = {'bar': 'quux'} acts like update and performs a merge is not obvious at all from the syntax.