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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 split(expr, frac, seed=None):
 """ Split the current column into two column objects with certain ratio. :param float frac: Split ratio :return: two split DataFrame objects """

    if hasattr(expr, '_xflow_split'):
        return expr._xflow_split(frac, seed=seed)
    else:
        return _split(expr, frac, seed=seed)