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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_step(self, step):
 """Add a step to the workflow. Args: step (Step):
 a step from the steps library. """

        self._closed()

        self.has_workflow_step = self.has_workflow_step or step.is_workflow
        self.wf_steps[step.name_in_workflow] = step