What wrong with my code? I think it works really fine, but I still got Bummer. (Task 4) --> (most_courses)

# 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.


def num_teachers(dictionary):
    length_dict = len(dictionary)
    return length_dict

def num_courses(dictionary):
    number = 0 
    for key in dictionary:
        lists = dictionary["{}".format(key)]
        real = len(lists)
        number += real
    print(number)
    return number

def courses(dictionary):
    result = []
    for key in dictionary:
        lists = dictionary["{}".format(key)]
        result.extend(lists)
        print(result)
    return result

def most_courses(dictionary):
    teacher = ''
    max_count = 0
    for key in dictionary:
        lists = dictionary["{}".format(key)]
        for value in lists:
            compare_count = len(value)
            if compare_count > max_count:
                max_count = compare_count
                teacher = key

    return teacher