How to use the yaml-ast-parser.dump function in yaml-ast-parser

pathInObjectTree.push(currentNode);
      for (let i = pathInObjectTree.length - 1; i > 0; i--) {
        if (_.keys(pathInObjectTree[i]).length > 0) {
          break;
        }
        _.unset(pathInObjectTree[i - 1], pathInYmlArray[i - 1]);
      }
    }

    const headObjectPath = _.head(pathInYmlArray);
    let newText = '';

    if (plainObject[headObjectPath]) {
      const newObject = {};
      newObject[headObjectPath] = plainObject[headObjectPath];
      newText = yaml.dump(newObject);
    }
    const beginning = yamlContent.substring(0, astObject[headObjectPath].parent.key.startPosition);
    const end = yamlContent.substring(astObject[pathInYml].endPosition, yamlContent.length);
    return fs.writeFileAsync(ymlFile, `${beginning}${newText}${end}`);
  }
  return BbPromise.resolve();
});

}
  }

  const arrayPropertyName = _.last(pathInYmlArray);
  let arrayProperty = currentNode[arrayPropertyName];
  if (_.isUndefined(arrayProperty) || _.isArray(arrayProperty)) {
    arrayProperty = arrayProperty || [];
  } else {
    throw new Error(`${arrayProperty} can only be undefined or an array!`);
  }
  currentNode[arrayPropertyName] = _.union(arrayProperty, [newValue]);

  const branchToReplaceName = _.head(pathInYmlArray);
  const newObject = {};
  newObject[branchToReplaceName] = plainObject[branchToReplaceName];
  const newText = yaml.dump(newObject);
  if (astObject[branchToReplaceName]) {
    const beginning = yamlContent
      .substring(0, astObject[branchToReplaceName].parent.key.startPosition);
    const end = yamlContent
      .substring(astObject[branchToReplaceName].endPosition, yamlContent.length);
    return fs.writeFileAsync(ymlFile, `${beginning}${newText}${end}`);
  }
  return fs.writeFileAsync(ymlFile, `${yamlContent}${os.EOL}${newText}`);
});