I'm not sure why my most_courses function isn't right. Its working in the external IDE i use to run practice code

# 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(dict):
    return len(dict)

def num_courses(dict):
    counter=0
    for keys in dict:
         if isinstance(dict[keys],list):
            counter+=len(dict[keys])
    return counter


def courses(dict):
    courses_offered=[]
    flattened=[]
    for keys in dict:
        courses_offered.append(dict[keys])
    for sublist in courses_offered:
        for val in sublist:
            flattened.append(val)
    return flattened

def most_courses(dict):
    return max(dict, key=dict.get)