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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 clean_sources(self):
 """Like clean, but also clears out files. """


        for src in self.dataset.sources:
            src.st_id = None
            src.t_id = None

        self.dataset.sources[:] = []
        self.dataset.source_tables[:] = []
        self.dataset.st_sequence_id = 1