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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 append_step(self, title, description, timestamp=None, data=None):
 """ Append a new provenance step. :param title: the title of the ProvenanceStep :type title: str :param description: the description of the ProvenanceStep :type description: str :param timestamp: the time of the ProvenanceStep :type timestamp: datetime, None, str :param data: The data of the ProvenanceStep :type data: dict :returns: the time of the ProvenanceStep :rtype: datetime """

        step = ProvenanceStep(title, description, timestamp, data)
        self._steps.append(step)
        return step.time