code: public static Set<LabelAtom> parse(String labels) {
          final Set<LabelAtom> r = new TreeSet<>();
          labels = fixNull(labels);
          if(labels.length()>0) {
              final QuotedStringTokenizer tokenizer = new QuotedStringTokenizer(labels);
              while (tokenizer.hasMoreTokens())
                  r.add(Jenkins.getInstance().getLabelAtom(tokenizer.nextToken()));
              }
          return r;
      }
docs: Convert a whitespace-separate list of tokens into a set of {@link Label}s.
  
  @param labels
  Strings like "abc def ghi". Can be empty or null.
  @return
  Can be empty but never null. A new writable set is always returned,
  so that the caller can add more to the set.
  @since 1.308