@Override
 public void subscriptionSucceeded(ValueRequirement requirement) {
   MarketDataProvider provider = _providerByRequirement.get(requirement);
   if (provider == _provider) {
     _combinedMarketDataProvider.subscriptionSucceeded(requirement);
   }
 }
 @Override
 public void subscriptionFailed(ValueRequirement requirement, String msg) {
   MarketDataProvider provider = _providerByRequirement.get(requirement);
   if (provider == _provider) {
     _combinedMarketDataProvider.subscriptionFailed(requirement, msg);
   }
 }
 @Override
 public void valuesChanged(Collection<ValueRequirement> requirements) {
   Map<MarketDataProvider, Set<ValueRequirement>> grouped = groupByProvider(requirements);
   Set<ValueRequirement> set = grouped.get(_provider);
   if (set != null) {
     _combinedMarketDataProvider.valuesChanged(set);
   }
 }