Function is_defined

lib/yamlcpp/include/yaml-cpp/node/detail/node_data.h:44–44

  void set_style(EmitterStyle::value style);

  bool is_defined() const { return m_isDefined; }
  const Mark& mark() const { return m_mark; }
  NodeType::value type() const {
    return m_isDefined ? m_type : NodeType::Undefined;