challenge task 5 where the hell i did wrong ? can any one explain me please

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.

teachers = {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'], 'Kenneth Love': ['Python Basics', 'Python Collections']}

def num_teachers(teachers):
    num = 0
    for d in teachers.keys():
        num = num + 1
    return num

def num_courses(teachers):
    total = 0
    for v in teachers.values():
        s = len(v)
        total = total + s
    return total

def courses(teachers):
    all_courses =[]
    for v in teachers.values():
        all_courses.extend(v)

    return all_courses

def most_courses(teachers):
    max_count = 0
    name = ""
    for teacher, course_list in teachers.items():
        if len(course_list) > max_count:
            max_count = len(course_list)
            name = teacher
    return name

def stats(teachers):
    list = []
    for teacher, course_list in teachers.items():
        another = [teacher, len(course_list)]
        list.append(another)

        return list