code: public static <T> Collection<T> asUnmodifiable(Collection<T> self) {
          return Collections.unmodifiableCollection(self);
      }
docs: Creates an unmodifiable view of a Collection.
  
  @param self a Collection
  @return an unmodifiable view of the Collection
  @see java.util.Collections#unmodifiableCollection(java.util.Collection)
  @see #asUnmodifiable(java.util.List)
  @since 2.5.0