static NLABlock nla_parse(S text) {
  ret nla_parse(new NLABlock(text));
}
  
// fills and returns original object
static NLABlock nla_parse(NLABlock nla) {
  // parse into lines (or sentences, both is OK)
  if (nla.lines == null)
    nla.lines = sentencesOrLines(nla.text);
    
  // get entities
  if (nla.entities == null) {
    new Matches m;
    nla.entities = linkedHashSet();
    for (S s : nla.lines)
      if "There is...|there are..." {
        S name = m.rest();
        NLABlock.Entity e = new(name, s);
        if (matchX2("a...|an...", name, m))
          e.addSynonym("the " + m.rest());
        nla.entities.add(e);
      }
  }
  
  // parse lines into fragments
  if (nla.parsedLines == null) {
    nla.parsedLines = new L;
    MapSO entitiesTree = listToWordTree(concatMap(nla.entities, e -> e.synonyms));
    for (int idx = 0; i < l(nla.lines); i++) {
      S s = nla.lines.get(idx);
      O parsed = parseToFragmentsUsingWordTree(s, entitiesTree);
      listPut(nla.parsedLines, idx, parsed);
    }
  }
  
  ret nla;
}