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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 cummin(self, axis=0, **kwargs):
 """ Cumulative min for each group. """

        if axis != 0:
            return self.apply(lambda x: np.minimum.accumulate(x, axis))

        return self._cython_transform('cummin', numeric_only=False)