keras-team/keras · error · ValueError

`stack` supports only `x` as list or tuple. Received: {type(

Error message

`stack` supports only `x` as list or tuple. Received: {type(x)}

What it means

Error "`stack` supports only `x` as list or tuple. Received: {type(x)}" thrown in keras-team/keras.

Source

Thrown at keras/src/backend/openvino/numpy.py:4426

    )
    split_lengths_tensor = ov_opset.constant(
        split_lengths, dtype=Type.i64
    ).output(0)

    axis_tensor = ov_opset.constant(axis, dtype=Type.i32).output(0)
    splits = ov_opset.variadic_split(x, axis_tensor, split_lengths_tensor)

    result = []
    for i in range(num_splits_val):
        result.append(OpenVINOKerasTensor(splits.output(i)))
    return result


def stack(x, axis=0):
    if isinstance(x, tuple):
        x = list(x)
    if not isinstance(x, list):
        raise ValueError(
            f"`stack` supports only `x` as list or tuple. Received: {type(x)}"
        )
    elems = [get_ov_output(e) for e in x]
    ref = elems[0]
    for i in range(1, len(elems)):
        ref, elems[i] = _align_operand_types(ref, elems[i], "stack()")
    elems[0] = ref
    const_axis = ov_opset.constant(axis, Type.i32).output(0)
    elems = [ov_opset.unsqueeze(e, const_axis).output(0) for e in elems]
    res = ov_opset.concat(elems, axis).output(0)
    return OpenVINOKerasTensor(res)


def std(x, axis=None, keepdims=False):
    var_x = var(x, axis, keepdims)
    std_dev = ov_opset.sqrt(var_x.output).output(0)
    return OpenVINOKerasTensor(std_dev)

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/backend/openvino/numpy.py:4426 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of keras-team/keras@7a34a03db6 (2026-08-25). Data as JSON: /api/errors/3d0a9c18aefadc9d. Report an issue: GitHub.