private String getAncestorString() {
        StringBuilder ret = new StringBuilder();
        ConfigDefinition ancestor = this;
        while (ancestor.getParent() != null) {
            ret.insert(0, ancestor.getName() + ".");
            ancestor = ancestor.getParent();
        }
        return ret.toString();
    }
Returns a string composed of the ancestors of this ConfigDefinition, skipping the root (which is the name
of the .def file). For example, if this is an array called 'leafArray' and a child of 'innerArray' which
is again a child of 'myStruct', then the returned string will be 'myStruct.innerArray.leafArray.'
The trailing '.' is included for the caller's convenience.

@return a string composed of the ancestors of this ConfigDefinition, not including the root
config/src/main/java/com/yahoo/vespa/config/ConfigDefinition.java