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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 get_rlz(self, rlzstr):
 r""" Get a Realization instance for a string of the form 'rlz-\d+' """

        mo = re.match(r'rlz-(\d+)', rlzstr)
        if not mo:
            return
        return self.realizations[int(mo.group(1))]