How to use the postcss/lib/input function in postcss

export default function lessParse (less, opts) {
  const input = new Input(less, opts);
  const parser = new LessParser(input, opts);
  // const parser = new Parser(input, opts);

  parser.tokenize();
  parser.loop();

  return parser.root;
}

let test = (css, tokens) => {
    expect(tokenize(new Input(css))).to.eql(tokens);
};

let test = (css, tokens) => {
    expect(tokenize(new Input(css))).to.eql(tokens);
};

function run(t, css, tokens) {
    t.deepEqual(tokenize(new Input(css)), tokens);
}

function testTokens (less, tokens) {
  expect(tokenize(new Input(less))).to.eql(tokens);
}

export default function parse (source, opts) {
  let input = new Input(source, opts)

  let parser = new Parser(input)
  parser.tokens = tokenizer(input)
  parser.parts = preprocess(input, liner(parser.tokens))
  parser.loop()

  return parser.root
}

export function parse(css: string, opts: Object) {
  let input = new Input(css, opts)

  let parser = new EmotionParser(input)
  parser.parse()

  return parser.root
}