def METHOD_NAME(self, name):
    """Get a sub class from a user provided class name or alias."""
    real_name = self._aliases.METHOD_NAME(name, name)
    try:
        sub_cls = self._sub_classes[real_name]
        return sub_cls
    except KeyError:
        print(f"{name} is not a valid sub-class of {self.base_cls}.")
        raise