Why it doesn't work?

# 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.keys())
def num_courses(dictionary):
    course_dict = {}
    for courses in dictionary.values():
        for course in courses:
            if course in course_dict:
                course_dict[course] += 1
            else:
                course_dict[course] = 1
    total = 0
    for value in course_dict.values():
        total += value
    return total
def courses(dictionary):
    course_dict = {}
    for courses in dictionary.values():
        for course in courses:
            course_dict[course] = 1
    return course_dict.keys()
def most_courses(dictionary):
    most = {"teacher": None, "Courses"=0}
    for teacher in dictionary.keys():
        teacher_courses = len(dictionary[teacher])
        if teacher_courses >= most["Courses"]:
            most["teacher"]=teacher
            most["Courses"]=teacher_courses
    return most["teacher"]