Checking if a value in a boost property tree is a tree or a terminal value

I have been looking for APIs in boost::property_tree (that is used for reading a json) that I can use to determine if a value of a field is a tree or a terminal value. For example, I have a json where the value of foo can either be a tree as illustrated in the first block or a string as illustrated in the second block.

{
    "foo": {
        " n1": "v1",
        "n2": "v2"
    }
}

{
    "foo": "bar"
}

I know we can check first with get_child_optional. If the returned value is null, then we can check get_optional. But are there any better ways/apis to do this?