private static MissingPolicy decodeMissingPolicy(Tokenizer tokenizer) {
        var policyName = tokenizer.token();
        try {
            return MissingPolicy.valueOf(policyName.toUpperCase());
        } catch (IllegalArgumentException e) {
            throw new IllegalInputException("Unknown missing policy '" + policyName +"' at " + tokenizer.spec());
        }
    }
Creates a new sorting from the given string and returns it, or returns null if the argument does not contain
any sorting criteria (e.g it is null or the empty string)
container-search/src/main/java/com/yahoo/search/query/Sorting.java