Programming FAQ about "How do you remove duplicates from a list?" -- Improve the examples + Mention possible caveats

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-04-20.21:53:49.898>
labels = ['type-feature', '3.8', '3.9', 'docs']
title = 'Programming FAQ about "How do you remove duplicates from a list?" -- Improve the examples + Mention possible caveats'
updated_at = <Date 2020-04-20.21:53:49.898>
user = 'https://github.com/Dominik1123'

bugs.python.org fields:

activity = <Date 2020-04-20.21:53:49.898>
actor = 'Dominik V.'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-04-20.21:53:49.898>
creator = 'Dominik V.'
dependencies = []
files = []
hgrepos = []
issue_num = 40347
keywords = []
message_count = 1.0
messages = ['366893']
nosy_count = 2.0
nosy_names = ['docs@python', 'Dominik V.']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue40347'
versions = ['Python 3.8', 'Python 3.9']