static RedundantCollectionOperationHandler handler(PsiMethodCallExpression call) {
      PsiMethodCallExpression qualifierCall = MethodCallUtils.getQualifierMethodCall(call);
      String replacementMethod;
      if (MAP_KEY_SET.test(qualifierCall)) {
        replacementMethod = "containsKey";
      }
      else if (MAP_VALUES.test(qualifierCall)) {
        replacementMethod = "containsValue";
      }
      else {
        return null;
      }
      PsiExpression mapExpression = qualifierCall.getMethodExpression().getQualifierExpression();
      if (mapExpression == null) return null;
      return new MapKeySetContainsHandler(replacementMethod);
    }
static RedundantCollectionOperationHandler handler(PsiMethodCallExpression call)