public ExpressionNode withTransformedExpressions(Function<ExpressionNode, ExpressionNode> transformer) {
        if (function instanceof ExpressionTensorFunction etf) {
            ExpressionNode orig = etf.expression;
            return transformer.apply(orig);
        }
        TensorFunction<Reference> transformed = function.withTransformedFunctions(fun -> transform(fun, transformer));
        return new TensorFunctionNode(transformed);
    }
Returns the tensor function wrapped by this
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java