list.count does not appear to function

[Oldman45]

I am learning about lists and apparently list.count does not function in the following:

mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
mylist.count(3)
print(mylist)

The output I get is

Output:
[5, 12, 27, 3, 12, 5, 9, 5, 11]

whereas it should return 1
When I use .insert, .reverse, .extend all is well!

Am I likely to have a problem with the Python package I am using?

I am using Windows 10 and Python 3.9.2

Any help would be appreciated