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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 nan_empty(self, col: str):
 """ Fill empty values with NaN values :param col: name of the colum :type col: str :example: ``ds.nan_empty("mycol")`` """

        try:
            self.df[col] = self.df[col].replace('', nan)
            self.ok("Filled empty values with nan in column " + col)
        except Exception as e:
            self.err(e, "Can not fill empty values with nan")