code: public synchronized @CheckForNull HashedToken findMatchingToken(@Nonnull String token) {
          String plainToken;
          if (isLegacyToken(token)) {
              plainToken = token;
          } else {
              plainToken = getHashOfToken(token);
          }
          
          return searchMatch(plainToken);
      }
docs: Search in the store if there is a token with the same secret as the one given
  @return {@code null} iff there is no matching token