@derived_from(pd.DataFrame)
    def cummin(self, axis=None, skipna=True):
        def aggregate(x, y):
            if isinstance(x, (pd.Series, pd.DataFrame)):
                return x.where((x < y) | x.isnull(), y, axis=1 - x.ndim)
            else:       # scalar
                return x if x < y else y
        cummin = lambda x, **kwargs: x.cummin(**kwargs)
        return self._cum_agg('cummin',
                             chunk=cummin,
                             aggregate=aggregate,
                             axis=axis, skipna=skipna,
                             chunk_kwargs=dict(axis=axis, skipna=skipna))
dataset/ETHPy150Open dask/dask/dask/dataframe/core.py/_Frame.cummin/swapped operands of `-`