Method contains

guava/src/com/google/common/collect/Maps.java:4176–4185

(@Nullable Object o)

    }

    @Override
    public boolean contains(@Nullable Object o) {
      if (o instanceof Entry) {
        Entry<?, ?> entry = (Entry<?, ?>) o;
        Object key = entry.getKey();
        V value = safeGet(map(), key);
        return Objects.equals(value, entry.getValue()) && (value != null || map().containsKey(key));
      }
      return false;
    }

    @Override
    public boolean isEmpty() {