public SchemaNode findFirstLeaf() {
        Node ret = this;
        while (ret.size() > 0) {
            ret = ret.get(0);
        }
        return ret.getSchemaNode();
    }
SchemaNode represents a node in the AST of a file the language server parses.
The node exposes a general interface to handle different AST from different parsers.
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/tree/SchemaNode.java