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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 choosers_columns_used(self):
 """ Columns from the choosers table that are used for filtering. """

        return list(tz.unique(tz.concatv(
            util.columns_in_filters(self.choosers_predict_filters),
            util.columns_in_filters(self.choosers_fit_filters))))