src/main/java/org/organicdesign/fp/collections/PersistentTreeMap.java
public static <K extends Comparable<K>,V> PersistentTreeMap<K,V>
    of(Iterable<Map.Entry<K,V>> es) {
        if (es == null) { return empty(); }
        PersistentTreeMap<K,V> map = new PersistentTreeMap<>(Equator.defaultComparator(), null, 0);
        for (Map.Entry<K,V> entry : es) {
            if (entry != null) {
                map = map.assoc(entry.getKey(), entry.getValue());
            }
        }
        return map;
    }
public static <K extends Comparable<K>,V> PersistentTreeMap<K,V>
    of(Iterable<Map.Entry<K,V>> es) {
        if (es == null) { return empty(); }
        PersistentTreeMap<K,V> map = new PersistentTreeMap<>(Equator.defaultComparator(), null, 0);
        for (Map.Entry<K,V> entry : es) {
            if (entry != null) {
                map = map.assoc(entry.getKey(), entry.getValue());
            }
        }
        return map;
    }
Returns a new PersistentTreeMap of the given comparable keys and their paired values, skipping
any null Entries.