Saving Layer Configs as JSON or YAML config files by representing the LayerConfig object as a dict and then turning into JSON/YAML wasn't working.

See issue here: https://github.com/aurelio-labs/semantic-router/issues/144

The issue was that, by attempting this, we were attempting to serialize all objects included in the Layer, including Routes, and the LLMs that those Routes use.

In the case of the above issue, the LLM was a Cohere one, which included a Client as one of its attributes, and this Client is not serializable.

So, instead of attempting to represent the entire LLM object a dict, to then be converted into JSON/YAML, we only keep key information about the LLM:

'module': self.llm.__module__,
'class': self.llm.__class__.__name__,
'model': self.llm.name

This is what's saved in route.py, and then sent to layer.py to be serialized (in LayerConfig.to_file()).

Then, when it comes time to load from the file via LayerConfig.from_file, the LLM is re-initialized dynamically.

Mostly just trying to make MyPy happy!

Also fixed bug in layer.py where we weren't:
a) Setting the index_name to a default value.
b) Weren't using index_name.

Making pydantic leave me alone and giving the correct index name.

Also made sure it's used properly in layer.py.

list_route_names for checking current route names.

remove for removing route and its associated data..

To tidy up __call__ in RouteLayer.

The test

TestRouteLayer::test_query_with_no_index

was failing because when it ran

assert route_layer("Anything").name is None

There were no Routes defined yet, and this meant that

route = [route for route in self.routes if route.name == top_class][0] was raising an error.

If no routes are defined then we can just defualt to RouteChoice().