@Contract("null -> null")
  private static PsiReferenceExpression getMapReferenceFromKeySetCall(PsiExpression keySetCandidate) {
    if (!(keySetCandidate instanceof PsiMethodCallExpression methodCallExpression)) return null;
    if (!MAP_KEY_SET.test(methodCallExpression)) return null;
    PsiExpression qualifier = methodCallExpression.getMethodExpression().getQualifierExpression();
    return tryCast(PsiUtil.skipParenthesizedExprDown(qualifier), PsiReferenceExpression.class);
  }
@Contract("null -> null")
  private static PsiReferenceExpression getMapReferenceFromKeySetCall(PsiExpression keySetCandidate)