node:internal/process/promises:227
          triggerUncaughtException(err, true /* fromPromise */);
          ^

TypeError [ERR_INVALID_ARG_TYPE]: The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received an instance of SourceMapGenerator
    at Object.writeFile (node:fs:1482:5)
    at /Users/.../build-css.js:46:12
    at processTicksAndRejections (node:internal/process/task_queues:93:5) {
  code: 'ERR_INVALID_ARG_TYPE'
}