code: @Override
      public void stage3SymbolVerification(final Document doc)
              throws SymbolWarning, IndexingFailure, ResourceDownloadError {
  
          final List<ResourceSyntaxWarning> exceptions =
                  new ArrayList<ResourceSyntaxWarning>();
  
          try {
              namespace.verify(doc);
          } catch (SymbolWarning e) {
              exceptions.addAll(e.getResourceSyntaxWarnings());
          }
  
          if (exceptions.isEmpty()) {
              return;
          }
  
          final String name = doc.getName();
          final String fmt = INVALID_SYMBOLS;
          final String msg = format(fmt, exceptions.size());
          throw new SymbolWarning(name, msg, exceptions);
      }
docs: {@inheritDoc}