public String getSecret(AccountIndex index) {
    Cursor cursor = getAccountCursor(index);
    try {
      if (!cursorIsEmpty(cursor)) {
        cursor.moveToFirst();
        return cursor.getString(cursor.getColumnIndex(SECRET_COLUMN));
      }
    } finally {
      tryCloseCursor(cursor);
    }
    return null;
  }
Tries to find the specified {@link AccountIndex} in the database, and failing that, will find
the first "similar" index in the database. Here, "similar" means that the index has a matching
non-null issuer and the stripped name of the account matches.

@see AccountIndex#getStrippedName()
@return the same {@code index} or a "similar" one with the same issuer that already exists
  in the database, or {@code null} if nothing similar is found
java/com/google/android/apps/authenticator/otp/AccountDb.java