I got always Invalid ruleset provided from bundleAndLoadRuleset

[jean13360]

I am using spectral and bundleAndLoadRuleset but when i load my rules , i always have an error Invalid ruleset

const {Spectral} = require('@stoplight/spectral-core');
const { bundleAndLoadRuleset } = require('@stoplight/spectral-ruleset-bundler/with-loader');

async function main() {
const spectral = new Spectral();
const myRuleset = [{ extends: "spectral:oas", rules: {} }];
// try to load an external ruleset
const fs = {
promises: {
async readFile(filepath) {
if (filepath === "/.spectral.yaml") {
return myRuleset;
}

      throw new Error(`Could not read ${filepath}`);
    },
  },
};

spectral.setRuleset(await bundleAndLoadRuleset("/.spectral.yaml", { fs, fetch }));
console.log(spectral)

}

if (require.main === module) {
main();
}

i am using
"@stoplight/spectral-core": "^1.16.1",
"@stoplight/spectral-ruleset-bundler": "^1.5.1",
"@stoplight/spectral-runtime": "^1.1.2",
and node 18.18.0
how to correct my ruleSet ?