def METHOD_NAME():
    grid = RasterModelGrid((4, 5))
    grid.status_at_node[13] = grid.BC_NODE_IS_FIXED_VALUE
    grid.status_at_node[2] = grid.BC_NODE_IS_CLOSED
    value_at_node = np.arange(grid.number_of_nodes, dtype=float)
    mat, rhs = get_core_node_matrix(grid, value_at_node)
    assert_array_equal(
        mat.toarray(),
        [
            [-4.0, 1.0, 0.0, 1.0, 0.0],
            [1.0, -3.0, 1.0, 0.0, 1.0],
            [0.0, 1.0, -4.0, 0.0, 0.0],
            [1.0, 0.0, 0.0, -4.0, 1.0],
            [0.0, 1.0, 0.0, 1.0, -4.0],
        ],
    )
    assert_array_equal(
        rhs,
        [[-6.0], [0.0], [-25.0], [-26.0], [-30.0]],
    )