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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 mmcif(self):
 """ Filepath for mmcif file associated with code. Notes ----- Downloads mmcif file if not already present. Returns ------- mmcif_file : str Filepath for the mmcif file. """

        mmcif_dir = os.path.join(self.parent_dir, 'mmcif')
        if not os.path.exists(mmcif_dir):
            os.makedirs(mmcif_dir)
        mmcif_file_name = '{0}.cif'.format(self.code)
        mmcif_file = os.path.join(mmcif_dir, mmcif_file_name)
        if not os.path.exists(mmcif_file):
            get_mmcif(code=self.code, outfile=mmcif_file)
        return mmcif_file