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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_cytoBand_hg19(self):
 """ Get UCSC cytoBand table for Build 37. Returns ------- pandas.DataFrame cytoBand table if loading was successful, else None """

        if self._cytoBand_hg19 is None:
            self._cytoBand_hg19 = self._load_cytoBand(self._get_path_cytoBand_hg19())

        return self._cytoBand_hg19