private static bool ValidateQuery(string query, out string[] queryParameters)
    {
        queryParameters = query.Split(' ');
        if (queryParameters.Length == 3)
        {
            if (queryParameters[0].ToLower() == "first_name" || queryParameters[0].ToLower() == "last_name" || queryParameters[0].ToLower() == "group")
            {
                if ( queryParameters[1] != "==" && queryParameters[1] != "<>")
                {
                    return false;
                }
                else return true;
            }
            else if (queryParameters[0].ToLower() == "rating" || queryParameters[0].ToLower() == "gpa")
            {
                if (!double.TryParse(queryParameters[2], out double k) || (queryParameters[1] != ">=" && queryParameters[1] != "<="))
                {
                    return false;
                }
                else return true;
            }
        }
        return false;
    }