code: def key_exists(self, namespace, key):
          
  
          return namespace in self.__data and key in self.__data[namespace]
docs: Checks a namespace for the existence of a specific key
  
          Args:
              namespace (str): Namespace to check in
              key (str): Name of the key to check for
  
          Returns:
              `True` if key exists in the namespace, else `False`