code: public static <K, V> Map<K, V> wrap(final Map<K, V> source) {
          if (source != null && !source.isEmpty()) {
              return new HashMap<>(source);
          }
          return new HashMap<>(0);
      }
docs: Wraps a possibly null map in an immutable wrapper.
  
  @param <K>    the key type
  @param <V>    the value type
  @param source map to wrap.
  @return the map