def col_swap(self, i, j):
        for k in range(0, self.rows):
            self[k, i], self[k, j] = self[k, j], self[k, i]
If C{since} is set, the attribute C{'since'} has a rendered timestamp.
dataset/ETHPy150Open sympy/sympy/sympy/matrices/dense.py/MutableDenseMatrix.col_swap--crossover with--dataset/ETHPy150Open ralphm/wokkel/wokkel/test/test_muc.py/HistoryOptionsTest.test_toElementSince