How to use the @react-native-firebase/app/lib/common.Base64.btoa function in @react-native-firebase/app

toBase64() {
    return Base64.btoa(this._binaryString);
  }

`firebase.storage.StorageReference.putString(_, *, _) 'format' provided is invalid, must be one of ${Object.values(
          StorageStatics.StringFormat,
        ).join(',')}.`,
      );
    }

    if (!isUndefined(metadata)) {
      validateMetadata(metadata);
    }

    let _string = string;
    let _format = format;
    let _metadata = metadata;

    if (format === StorageStatics.StringFormat.RAW) {
      _string = Base64.btoa(_string);
      _format = StorageStatics.StringFormat.BASE64;
    } else if (format === StorageStatics.StringFormat.DATA_URL) {
      const { mediaType, base64String } = getDataUrlParts(_string);
      if (isUndefined(base64String)) {
        throw new Error(
          'firebase.storage.StorageReference.putString(*, _, _) invalid data_url string provided.',
        );
      }

      if (isUndefined(metadata) || isUndefined(metadata.contentType)) {
        if (isUndefined(metadata)) {
          _metadata = {};
        }
        _metadata.contentType = mediaType;
        _string = base64String;
        _format = StorageStatics.StringFormat.BASE64;