The fourth question of this code challenge works in workspaces but not in the code challenge... what's wrong?

# 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):
    return len(dictionary)

def num_courses(dictionary):
    num = 0
    for value in dictionary.values():
        num += len(value)
    return num

def courses(dictionary):
    courses = []
    for value in dictionary.values():
        courses += value
    return courses

def most_courses(dictdef most_courses(dictionary):
    new_courses = {n: len(dictionary[n]) for n in dictionary.keys()}
    return list(new_courses.keys())[list(new_courses.values()).index(max(new_courses.values()))]