// e.g. "I am <vague height>" to "I am *"
// var names will be stripped of angle brackets
sS angleBracketVarsToStars(S s, LS varNames_out default null) {
  LS tok = javaTokWithAngleBrackets(s);
  for (int idx : indicesOfAngleBracketVars(tok)) {
    varNames_out?.add(deAngleBracket(tok.get(idx)));
    tok.set(idx, "*");
  }
  ret join(tok);
}