Syntax error?

def num_teachers(a_dict):
    return len(a_dict)

def num_courses(a_dict):
    total = 0
    for value in a_dict.values():
        total += len(value)
    return total

def courses(a_dict):
    my_list = []
    for course in a_dict.values():
        my_list += course
    return my_list

def most_courses(a_dict):
    maximus = 0
    for teacher, course in a_dict.items():
        if len(course) > maximus:
            maximus = len(course)
            teacher_name = teacher
    return teacher_name

def stats(a_dict):
    my_list = []
    for teacher, course in a_dict.items():
        my_list.append([teacher, len(course)])
    return my_list