Add function to model_lya that defines the set of possible default models (their names, and a bit of description of where the data comes from). Throw an error if Theory is not passed exactly one of these names, and tell the user what the options are.
Add function to model_lya that defines the set of possible default models (their names, and a bit of description of where the data comes from). Throw an error if Theory is not passed exactly one of these names, and tell the user what the options are.