Converting Option to Effect in Effect.gen

const eff = Effect.gen(function* () {
  const contentType = yield* pipe(
    selectionDataUrl,
    String.split(","),
    Array.head,
    Option.map(String.replace(";base64", "")),
    Option.map(String.slice(String.length("data:"))),
    // what should I had here so my Option<string> become Effect<string, ContentTypeCantBeDeduced> 
  );
});