@Nullable
 private static PsiElement addFieldToSetUp(
     PyClass clazz, final Function<String, PyStatement> callback) {
   final PyFunction init =
       clazz.findMethodByName(PythonUnitTestUtil.TESTCASE_SETUP_NAME, false, null);
   if (init != null) {
     return AddFieldQuickFix.appendToMethod(init, callback);
   }
   final PyFunctionBuilder builder =
       new PyFunctionBuilder(PythonUnitTestUtil.TESTCASE_SETUP_NAME, clazz);
   builder.parameter(PyNames.CANONICAL_SELF);
   PyFunction setUp = builder.buildFunction(clazz.getProject(), LanguageLevel.getDefault());
   final PyStatementList statements = clazz.getStatementList();
   final PsiElement anchor = statements.getFirstChild();
   setUp = (PyFunction) statements.addBefore(setUp, anchor);
   return AddFieldQuickFix.appendToMethod(setUp, callback);
 }