teacher stats task 3 of 5. Somebody help! I'm stuck

# 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(treehouse):
    treehouse_key =   treehouse.keys()
    return len(treehouse_key)

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

def courses(treehouse):
    the_list = []
    for tree in treehouse:
        the_list.extend(treehouse[tree])
        return the_list