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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 merge_regions(self, id1, id2):
 """Merge two regions into one. The merged region will take on the id1 identifier. :param id1: region 1 identifier :param id2: region 2 identifier """

        region2 = self.region_by_identifier(id2)
        self[region2] = id1