code: public static <T> T callInTransaction(final ConnectionSource connectionSource, final Callable<T> callable)
  			throws SQLException {
  		return callInTransaction(null, connectionSource, callable);
  	}
docs: Same as {@link #callInTransaction(Callable)} except as a static method with a connection source.
  
  <p>
  WARNING: it is up to you to properly synchronize around this method if multiple threads are using a
  connection-source which works gives out a single-connection. The reason why this is necessary is that multiple
  operations are performed on the connection and race-conditions will exist with multiple threads working on the
  same connection.
  </p>