This function is used to register a mode for a model.
Details
This function can be called multiple times without error. This becomes
valuable when multiple packages adds the same mode to a model. Having both
packages use set_model_mode()
avoids having one package depend on the
other.
Examples
if (FALSE) {
set_new_model("shallow_learning_model")
get_from_env("shallow_learning_model_modes")
set_model_mode("shallow_learning_model", "partition")
get_from_env("shallow_learning_model_modes")
}