presto-main/src/main/java/io/prestosql/sql/planner/LocalExecutionPlanner.java/LocalExecutionPlanner/getChannelsForSymbols
class LocalExecutionPlanner:    private static List<Integer> getChannelsForSymbols(List<Symbol> symbols, Map<Symbol, Integer> layout)
    {
        ImmutableList.Builder<Integer> builder = ImmutableList.builder();
        for (Symbol symbol : symbols) {
            builder.add(layout.get(symbol));
        }
        return builder.build();
    }