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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_genetic_map_HapMapII_GRCh37(self):
 """ Get International HapMap Consortium HapMap Phase II genetic map for Build 37. Returns ------- dict dict of pandas.DataFrame HapMapII genetic maps if loading was successful, else None """

        if self._genetic_map_HapMapII_GRCh37 is None:
            self._genetic_map_HapMapII_GRCh37 = self._load_genetic_map(
                self._get_path_genetic_map_HapMapII_GRCh37()
            )

        return self._genetic_map_HapMapII_GRCh37