Verifies eval shared models and normnalizes to produce a single list.
) -> Optional[List[types.EvalSharedModel]]
The output is normalized such that if a list or dict contains a single entry,
the model name will always be empty.
None, a single model, a list of models, or a dict of
models keyed by model name.
A list of models or None.
ValueError if dict is passed and keys don't match model names or a
multi-item list is passed without model names.