code: def split(self, frac):
          
          from .. import preprocess
          split_obj = getattr(preprocess, '_Split')(fraction=frac)
          return split_obj.transform(self)
docs: Split the DataFrame into two DataFrames with certain ratio.
  
          :param frac: Split ratio
          :type frac: float
  
          :return: two split DataFrame objects
          :rtype: list[DataFrame]