def combine_op_type(node: _fx.Node) -> _Optional[CombinationOpType]:
    """
    Returns type of combination op at this node -> add, mul, add-relu or concat
    """
    if is_add(node):
        return CombinationOpType.Add
    elif is_mul(node):
        return CombinationOpType.Mul
    elif is_add_relu(node):
        return CombinationOpType.AddReLU
    elif is_concat(node):
        return CombinationOpType.Concat
    return None

    Returns type of combination op at this node -> add, mul, add-relu or concat
    
coremltools/optimize/torch/quantization/_utils.py