loadYamlNode function
Loads a single document from a YAML string as a YamlNode.
This is just like loadYaml, except that where loadYaml would return a normal Dart value this returns a YamlNode instead. This allows the caller to be confident that the return value will always be a YamlNode.
Implementation
YamlNode loadYamlNode(String yaml,
        {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener}) =>
    loadYamlDocument(yaml,
            sourceUrl: sourceUrl,
            recover: recover,
            errorListener: errorListener)
        .contents;