private boolean checkIndent(ISet o) {
   if (indent && o.size() > 1) {
     for (IValue x : o) {
       Type type = x.getType();
       return indented(type);
     }
   }
   return false;
 }
  public ITree filterAmbiguity(ITree ambCluster, Object environment) {
    ISet alts = (ISet) ambCluster.get("alternatives");

    if (alts.size() == 0) {
      return null;
    }

    Environment env = (Environment) environment;

    Result<IValue> var = env.getFrameVariable("amb");

    if (var != null && var instanceof ICallableValue) {
      Type type = RascalTypeFactory.getInstance().nonTerminalType(ambCluster);
      ICallableValue func = (ICallableValue) var;
      try {
        Result<IValue> result = func.call(new Type[] {TF.setType(type)}, new IValue[] {alts}, null);

        if (result.getType().isBottom()) {
          return ambCluster;
        }
        ITree r = (ITree) result.getValue();
        if (TreeAdapter.isAmb(r)) {
          ISet returnedAlts = TreeAdapter.getAlternatives(r);
          if (returnedAlts.size() == 1) {
            return (ITree) returnedAlts.iterator().next();
          } else if (returnedAlts.size() == 0) {
            return null;
          } else {
            return r;
          }
        }

        return (ITree) result.getValue();
      } catch (ArgumentMismatch e) {
        return ambCluster;
      }
    }

    return ambCluster;
  }