public @NotNull <T> Builder add(@NotNull DataKey<? super T> dataKey, @Nullable T value) {
      if (value != null) {
        if (myMap == null) myMap = new HashMap<>();
        myMap.put(dataKey.getName(), value);
      }
      return this;
    }
public @NotNull <T> Builder add(@NotNull DataKey<? super T> dataKey, @Nullable T value)