public List<String> get(String name) {
        List<Object> values = properties.get(name);
        if (values == null) return null;
        if (values.isEmpty()) return Collections.<String>emptyList();

        // Compatibility ...
        List<String> stringValues = new ArrayList<>(values.size());
        for (Object value : values)
            stringValues.add(value.toString());
        return Collections.unmodifiableList(stringValues);
    }
Returns a read-only list of properties by full name.
If this is not set, null is returned. If this is explicitly set to
have no values, and empty list is returned.
container-search/src/main/java/com/yahoo/search/query/ranking/RankProperties.java