public Symbol setSymbol(SymbolType type, String fileURI) {
        if (this.hasSymbol()) {
            throw new IllegalArgumentException("Cannot set symbol for node: " + this.toString() + ". Already has symbol.");
        }
        this.symbol = new Symbol(this, type, fileURI);

        return symbol;
    }
Returns the next sibling of this schema node.
A sibling node is a node that shares the same parent node.

@return the next sibling of this schema node, or null if there is no previous sibling
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/tree/Node.java