def _combine(self, datas, function):
        data = datas[0]
        data = data.astype('float64')
        for d in datas[1:]:
            if isinstance(d, DataFrame):
                if len(d.columns) == 1:
                    d = d[d.columns[0]]
                else:
                    raise NotImplementedError
            cols = [(c, d.name) % '%s, %s' for c in data.columns]
            data = function(data, d.astype('float64'), axis=0)
            data = data.fillna(self.fillna)
            data.columns = cols
        return data
dataset/ETHPy150Open kvh/ramp/ramp/features/combo.py/ComboMap._combine/swapped operands of `%`