@staticmethod
def addable_cells(obj):
    """
        No cell should be added in isolation
        except for vectors

        TESTS ::

            sage: from sage.matrix.constructor import Matrix
            sage: from sage_widget_adapters.matrix.matrix_grid_view_adapter import MatrixGridViewAdapter
            sage: m = Matrix(QQ, 2, 3, range(6))/2
            sage: MatrixGridViewAdapter.addable_cells(m)
            []
        """
    if obj.nrows() == 1:
        return [(0, obj.ncols())]
    if obj.ncols() == 1:
        return [(obj.nrows(), 0)]
    return []
