code: public ProductPartitionNode putCustomParameter(String key, String value) {
      if (!nodeState.supportsCustomParameters()) {
        throw new IllegalStateException(
            String.format("Cannot set custom parameters on a %s node", nodeState.getNodeType()));
      }
      this.nodeState.getCustomParams().put(key, value);
      return this;
    }
docs: Puts the specified key/value pair in the map of custom parameters.
  @throws IllegalStateException if this node is not a biddable UNIT node