How to use the yaml.parseCST function in yaml

parseAST (text: string) {
    const cst = YAML.parseCST(text)
    cst.setOrigRanges() // Workaround for CRLF eol, https://github.com/eemeli/yaml/issues/127
    const doc = new YAML.Document({ keepCstNodes: true }).parse(cst[0])

    const findPairs = (node: YAML.ast.AstNode | YAML.ast.Pair | null, path: string[] = []): KeyInDocument[] => {
      if (!node)
        return []
      if (node.type === 'MAP' || node.type === 'SEQ')
      // @ts-ignore
        return _.flatMap(node.items, m => findPairs(m, path))
      if (node.type === 'PAIR' && node.value != null && node.key != null) {
        if (!['BLOCK_FOLDED', 'BLOCK_LITERAL', 'PLAIN', 'QUOTE_DOUBLE', 'QUOTE_SINGLE'].includes(node.value.type)) {
          return findPairs(node.value, [...path, node.key.toString()])
        }
        else {
          const valueCST = node.value.cstNode
          if (!valueCST || !valueCST.valueRange)