Add parameter metadata to the trainer schema.

[justinxzhao]

No description provided.

[github-actions]

Unit Test Results

       6 files  ±0         6 suites  ±0   2h 40m 38s ⏱️ + 3m 28s
2 908 tests ±0  2 862 ✔️ ±0    46 💤 ±0  0 ❌ ±0 
8 724 runs  ±0  8 582 ✔️ ±0  142 💤 ±0  0 ❌ ±0 

Results for commit 48023a3. ± Comparison against base commit 9d7da5f.

♻️ This comment has been updated with latest results.

[ksbrar]

I would still keep {} as the default value for default so it's visually clear that in the case of GradientClippingDataclassField an empty dict is valid (whereas e.g. for OptimizerDataclassField you have to at least provide a type inside the dict)

[justinxzhao]

Added back the default value for default for now.

Outside of this PR, we should consider removing the default values for marshmallow field function arguments. This will make some of the marshmallow unit tests more verbose, but it ensures that the field's parameters (default, description, etc.) are defined in one location, at the point of instantiation. For example, right now for OptimizerDataclassField, we declare the default in two places -- as a function parameter default via the marshmallow field definition, as well as at the point of instantiation in ECDTrainerConfig.

Here's what I'm thinking:

• Always include description and default as required arguments so that it's impossible to instantiate a marshmallow field without explicitly specifying the description and default. This setup ensures that the defaults and descriptions are concisely listed where parameters are declared, i.e. ECDTrainerConfig.
• Include other arguments like allow_none in the marshmallow field only if we want this to be able to be configured differently across different instances of the field. For example, we should remove allow_none from the list of parameters for GradientClippingDataclassField since it's always True.
• Use ParameterMetadata to contain all other "optional" information pertaining to the field. Eventually, this will also be a required argument.

See also, why default arguments are bad.

[ksbrar]

Agreed on all counts!