public void setIncludeFields(List<String> includeFields) {
        Set<String> keys = ConcurrentHashMap.newKeySet(includeFields.size());
        keys.addAll(includeFields);
        this.includeFields = Collections.unmodifiableSet(keys);
    }
Factory class for {@link StandardWriteFilter}. See that class
for how the estimated sizes are calculated on Strings.
tika-core/src/main/java/org/apache/tika/metadata/writefilter/StandardWriteFilterFactory.java