static L<GazelleTree> gazelle_reasonWithPreprocessing(S input1, O... _) {
  F0<GazelleEvalContext> contextMaker = cast assertNotNull("Need contextMaker", optPar contextMaker(_));
  S userName = stringPar userName(_);
  bool debug = boolPar debug(_);
  bool debugPreprocessing = boolPar debugPreprocessing(_);
  
  Collection<GInterpretable> interpretables = gazelle_preprocess(input1, _);
  
  if (debugPreprocessing) {
    print("Got " + n2(interpretables, "interpretable") + ".");
    printIndentLines(interpretables);
  }
  
  Set<S> acceptablePurposes = cast optPar acceptablePurposes(_);
  if (acceptablePurposes == null) acceptablePurposes = litset("");
  
  new L<GazelleTree> l2;
  Set<S> outputs = ciSet();
  for (GInterpretable intp : interpretables)
    for (GazelleTree tree : dm_gazelle_reasonAboutChatInput_v2(userName, intp.text, paramsPlus(_, +acceptablePurposes)))
      if (outputs.add(tree.line))
        l2.add(tree);
  ret l2;
}