@SuppressWarnings("unchecked")
  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(
      K k1, V v1, K k2, V v2) {
    return ofEntries(entryOf(k1, v1), entryOf(k2, v2));
  }
@SuppressWarnings("unchecked")
  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(
      K k1, V v1, K k2, V v2) {
    return ofEntries(entryOf(k1, v1), entryOf(k2, v2));
  }
@ SuppressWarnings ( "unchecked" ) public static < K extends Comparable < ? super K > , V > ImmutableSortedMap < K , V > of ( K k1 , V v1 , K k2 , V v2 ) { return ofEntries ( entryOf ( k1 , v1 ) , entryOf ( k2 , v2 ) ) ; }
Returns an immutable sorted map containing the given entries, sorted by the natural ordering of
their keys.

@throws IllegalArgumentException if the two keys are equal according to their natural ordering
Returns an immutable sorted map containing the given entries sorted by the natural ordering of their keys .