How to use the @yarnpkg/parsers.parseShell function in @yarnpkg/parsers

const normalizedEnv: {[key: string]: string} = {};
  for (const [key, value] of Object.entries(env))
    if (typeof value !== `undefined`)
      normalizedEnv[key] = value;

  const normalizedBuiltins = new Map(BUILTINS);
  for (const [key, builtin] of Object.entries(builtins))
    normalizedBuiltins.set(key, builtin);

  // This is meant to be the equivalent of /dev/null
  if (stdin === null) {
    stdin = new PassThrough();
    (stdin as PassThrough).end();
  }

  const ast = parseShell(command);

  // If the shell line doesn't use the args, inject it at the end of the
  // right-most command
  if (!locateArgsVariable(ast) && ast.length > 0 && args.length > 0) {
    let command = ast[ast.length - 1];
    while (command.then)
      command = command.then.line;

    let chain = command.chain;
    while (chain.then)
      chain = chain.then.chain;

    if (chain.type === `command`) {
      chain.args = chain.args.concat(args.map(arg => {
        return {
          type: `argument` as 'argument',