private static int sum(Collection<Integer> integers) {
        int sum = 0;
        for (int integer : integers)
            sum += integer;
        return sum;
    }
Computes the following elementCompleteness features:
<ul>
    <li><code>completeness</code>
    <li><code>fieldCompleteness</code>
    <li><code>queryCompleteness</code>
    <li><code>elementWeight</code>
</ul>

@param queryTerms the query terms with associated weights to compute over
@param field a set of weighted field values, where each is taken to be a space-separated string of tokens
@return a features object containing the values listed above
searchlib/src/main/java/com/yahoo/searchlib/ranking/features/ElementCompleteness.java