@Override
 public Convention getConvention(final UniqueId identifier) {
   final ConventionDocument doc = _conventionMaster.getConvention(identifier);
   if (doc != null) {
     return doc.getValue();
   }
   return null;
 }
 @Override
 public Convention getConvention(final ExternalIdBundle identifiers) {
   final ConventionSearchResult result =
       _conventionMaster.searchConvention(new ConventionSearchRequest(identifiers));
   final int size = result.getResults().size();
   switch (size) {
     case 0:
       return null;
     case 1:
       return Iterables.getOnlyElement(result.getResults()).getValue();
     default:
       throw new OpenGammaRuntimeException(
           "Multiple matches (" + size + ") to " + identifiers + "; expecting one");
   }
 }