DISCUSS: on branch dll in file test_dbl_linked_list.py shorten code to refer directly to the fixture and not assign it again

[wenima]

def test_push_empty_list(create_empty_dbl_ll):
    """Test pushed val is new head and tail."""
    dll = create_empty_dbl_ll
    dll.push(5)
    assert dll.head.value == 5 and dll.tail.value == 5

the dll = here is redundant if we directly ref the fixture. I know that it was done to keep names short but better then to change name of fixture. Your thoughts?