svoid test_positionalTokenIndex2_filter() {
  PositionalTokenIndex2 idx = positionalTokenIndex2_wordTok(tlft([[
    you are here
    what is this
    hello world
    hello you
  ]]));
  assertEqualsVerbose(ll("you are here"), map join(
    positionalTokenIndex_filter(idx, "you * *")));
  // index should preserve original order
  assertEqualsVerbose(ll("hello world", "hello you"), map join(idx.byToken(0, "hello")));
  assertEqualsVerbose(ll("what is this"), map join(idx.byToken(1, "is")));
  assertEqualsVerbose(ll(), unnull(map join(idx.byToken(3, "is"))));

}