@Override
        public String toString(ToStringContext<Reference> c) {
            ToStringContext<Reference> outermost = c;
            while (outermost.parent() != null)
                outermost = outermost.parent();

            if (outermost instanceof ExpressionToStringContext context) {
                ExpressionNode root = expression;
                if (root instanceof CompositeNode && ! (root instanceof EmbracedNode) && ! isIdentifierReference(root))
                    root = new EmbracedNode(root); // Output embraced if composite
                return root.toString(new StringBuilder(),
                                     new ExpressionToStringContext(context.wrappedSerializationContext, c, context.path, context.parent),
                                     context.path,
                                     context.parent).toString();
            }
            else {
                return expression.toString();
            }
        }
Returns the tensor function wrapped by this
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java