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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 from_source(self, checkpoint):
 """ Creates a new Checkpoint from an existing checkpoint. :param checkpoint: Existing checkpoint. :type checkpoint: ~azure.eventprocessorhost.checkpoint.Checkpoint """

        self.partition_id = checkpoint.partition_id
        self.offset = checkpoint.offset
        self.sequence_number = checkpoint.sequence_number