Steps to Reproduce

persistence = PicklePersistence('my_file', store_user_data=True, store_chat_data=True, store_bot_data=True, on_flush=False)
After running persistence.update_user_data(update.message.from_user.id, user_data), the previous user_data is restored, thus having no effect on the persistence and making it unusable

Expected behaviour

self.user_data should be saved after running persistence.update_user_data without restoring the previous data

Actual behaviour

After running persistence.update_user_data , dispatcher is calling __update_persistence.
on line 729, the code runs over the new saved data with the old saved data:
self.persistence.update_user_data(user_id, self.user_data[user_id]),

Operating System

Windows

Version of Python, python-telegram-bot & dependencies

Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 23:11:46) [MSC v.1916 64 bit (AMD64)] on win32

python-telegram-bot 13.7
Bot API 5.3
certifi 2020.12.05
Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 23:11:46) [MSC v.1916 64 bit (AMD64)]

Relevant log output

No response

Additional Context

No response