Method cols

tests/test_buffers.cpp:250–250

        py::ssize_t rows() const { return Matrix::rows() / m_row_factor; }
        py::ssize_t cols() const { return Matrix::cols() / m_col_factor; }
        py::ssize_t row_factor() const { return m_row_factor; }
        py::ssize_t col_factor() const { return m_col_factor; }