def grade_an_submission(cls):
     """
     method change the argument (grade) of object from submissions list
     """
     Ui.print_submissions_list(Submission.submission_list,
                               "Submission list:")
     sub_to_grade = Ui.get_inputs(
         ['Submission name: ', 'ID: '],
         'Type submission name, and student ID which you want to grade: \n')
     found = False
     for sub in Submission.submission_list:
         if sub.name == sub_to_grade[0] and sub.student_id == sub_to_grade[
                 1]:
             found = True
             if found:
                 Ui.print_message(
                     "Chosen submission:\n{} {} {} {} {}\n".format(
                         sub.send_date, sub.name, sub.grade,
                         sub.github_link, sub.student_id))
                 sub_grade = Ui.get_inputs(['Grade: '], "Type the grade: ")
                 sub.grade = sub_grade[0]
                 Ui.print_message('Submission graded!')
     if not found:
         Ui.print_message('Wrong submission name or ID')