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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 sample(self, fraction, seed=None, exact=False):
 """ Sample a fraction of the current SFrame's rows. Parameters fraction : float Fraction of the rows to fetch. Must be between 0 and 1. if exact is False (default), the number of rows returned is approximately the fraction times the number of rows. seed : int, optional Seed for the random number generator used to sample. exact: bool, optional Defaults to False. If exact=True, an exact fraction is returned, but at a performance penalty. Returns ------- out : SFrame A new SFrame containing sampled rows of the current SFrame. Examples -------- Suppose we have an SFrame with 6,145 rows. Retrieve about 30% of the SFrame rows with repeatable results by setting the random seed. 1783 """

        if seed is None:
            seed = abs(hash("%0.20f" % time.time())) % (2 ** 31)

        if (fraction > 1 or fraction < 0):
            raise ValueError('Invalid sampling rate: ' + str(fraction))


        if (self.num_rows() == 0 or self.num_columns() == 0):
            return self
        else:
            with cython_context():
                return SFrame(_proxy=self.__proxy__.sample(fraction, seed, exact))