code: def get_commands(self, namespace):
          
          if not namespace:
              # Default name space:
              namespace = DEFAULT_NAMESPACE
  
          try:
              namespace.strip().lower()
              commands = list(self._commands[namespace].keys())
              commands.sort()
              return commands
          except KeyError:
              # Unknown name space
              return []
docs: Retrieves the commands of the given name space. If *namespace* is None
          or empty, it retrieves the commands of the default name space
  
          :param namespace: The commands name space
          :return: A list of commands names