protected final @Nullable Object getValue(Property property) throws Exception {
    int size = myContainers.size();
    if (size == 0) {
      return null;
    }

    Object value = property.getValue(myContainers.get(0));
    for (int i = 1; i < size; i++) {
      if (!Comparing.equal(value, property.getValue(myContainers.get(i)))) {
        return null;
      }
    }

    return value;
  }
protected final @Nullable Object getValue(Property property)