def get_device_model(self, cat, sub_cat, key=''):
        """Return the model name given cat/subcat or product key"""
        if cat + ':' + sub_cat in self.device_models:
            return self.device_models[cat + ':' + sub_cat]
        else:
            for i_key, i_val in self.device_models.items():
                if 'key' in i_val:
                    if i_val['key'] == key:
                        return i_val
            return False
Return the model name given cat/subcat or product key