valuesBuilder.add(requireNonNull(stream.readObject()));
      }
      ImmutableSet<Object> valueSet = valuesBuilder.build();
      if (valueSet.size() != valueCount) {
        throw new InvalidObjectException("Duplicate key-value pairs exist for key " + key);
      }
      builder.put(key, valueSet);
      tmpSize += valueCount;
    }

    ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
    try {