code: static boolean containsAllImpl(Collection<?> self, Collection<?> c) {
      return Iterables.all(c, Predicates.in(self));
    }
docs: Returns {@code true} if the collection {@code self} contains all of the
  elements in the collection {@code c}.
  
  <p>This method iterates over the specified collection {@code c}, checking
  each element returned by the iterator in turn to see if it is contained in
  the specified collection {@code self}. If all elements are so contained,
  {@code true} is returned, otherwise {@code false}.
  
  @param self a collection which might contain all elements in {@code c}
  @param c a collection whose elements might be contained by {@code self}