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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 max(self):
 """Maximum, ignorning nans."""

        if "max" not in self.attrs.keys():

            def f(dataset, s):
                return np.nanmax(dataset[s])

            self.attrs["max"] = np.nanmax(list(self.chunkwise(f).values()))
        return self.attrs["max"]