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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_task_file_manager(self, task_file_manager):
 """ Add a task file manager. Only available after that the Plugin Manager is loaded """

        if not self._loaded:
            raise PluginManagerNotLoadedException()
        self._task_factory.add_custom_task_file_manager(task_file_manager)