Removing Non-Duplicated Items from List (python)

I have this list:

mylist = [['TX', 'DALLAS'],
 ['TX', 'DALLAS'],
 ['CA', 'LA'],
 ['CA', 'LA'],
 ['ID', 'BOISE']],

I’ve been trying to write a loop that makes a new list containing only those that were duplicates.

This is my current code:

for i in mylist:
  if mylist.count(i) > 1:
    mylist.remove(i)

mylist

my output:

[['TX', 'DALLAS'], ['CA', 'LA'], ['ID', 'BOISE']]

So the output would be:

[['TX', 'DALLAS'], ['CA', 'LA']],

>Solution :

list_of_lists = [['TX', 'DALLAS'],
                 ['TX', 'DALLAS'],
                 ['CA', 'LA'],
                 ['CA', 'LA'],
                 ['ID', 'BOISE']]

duplicates = []

for item in list_of_lists:
    if list_of_lists.count(item) > 1 and item not in duplicates:
        duplicates.append(item)

print(duplicates)