can anyone explain why this function didn't pass? i tried so much i created another function...

# 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(a_dict):
    return len(a_dict.keys())



def num_courses(a_dict):
    count = 0
    for teacher in a_dict:
        count += len(a_dict[teacher])
    return count    


def courses(a_dict):
    new = []
    for key,value in a_dict.items():
        for values in a_dict[key]:
            new.append(values)
    return new  


def most_courses(teachers_info):
    max_count = 0
    for teacher, courses in teachers_info.items():
        if len(courses) > max_count:
            max_count = len(courses)
            max_teacher = teacher
    return max_teacher        

def stats(a_dict):
    teach_list = []
    for teachers,classes in a_dict.items():
        teachers = teachers.split(':')
        teachers.append(len(classes))
        teach_list.append(teachers)
    return teach_list