public String expectLiteral() {
        if (!isStatic()) {
            throw new RuntimeException("Expected a literal when not all parts are literals.");
        }
        return value;
    }
Returns the literal value of this template, throwing
{@link RuntimeException} if the template is not static.

@return returns the string literal value.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/language/syntax/expressions/Template.java