presto-main/src/main/java/io/prestosql/cost/CostCalculatorUsingExchanges.java/CostCalculatorUsingExchanges/CostCalculatorUsingExchanges
class CostCalculatorUsingExchanges:    @Inject
    public CostCalculatorUsingExchanges(TaskCountEstimator taskCountEstimator)
    {
        this.taskCountEstimator = requireNonNull(taskCountEstimator, "taskCountEstimator is null");
    }