Function value_builder

cpp/src/arrow/array/builder_nested.h:607–607

\brief Get builder to add Map entries as struct values. This is used instead of key_builder()/item_builder() and allows the Map to be built as a list of struct values.

  /// This is used instead of key_builder()/item_builder() and allows
  /// the Map to be built as a list of struct values.
  ArrayBuilder* value_builder() const { return list_builder_->value_builder(); }

  std::shared_ptr<DataType> type() const override {
    // Key and Item builder may update types, but they don't contain the field names,