code: private Collection<Node> checkNegationSpecifier(final NegationSpecifier specifier) throws NodeSelectorException {
  		Collection<Selector> parts = new LinkedHashSet<Selector>(1);
  		parts.add(specifier.getSelector());
  		return check(parts);
  	}
docs: Check the {@link NegationSpecifier}.
  <p/>
  This method will add the {@link Selector} from the specifier in
  a list and invoke {@link #check(List)} with that list as the argument.
  
  @param specifier The negation specifier.
  @return A set of nodes after invoking {@link #check(List)}.
  @throws NodeSelectorException In case of an error.