I have a .txt file that contains the string `"2020-08-13T20:41:15.4227628Z"`
What format code should I use in `strptime` function in Python 3.7? I tried the following but the `'8'` at end just before `'Z'` is not a valid weekday

```
from datetime import datetime

timestamp_str = "2020-08-13T20:41:15.4227628Z"
timestamp = datetime.strptime(timestamp_str, '%Y-%m-%dT%H:%M:%S.%f%uZ')

ValueError: time data '2020-08-13T20:41:15.4227628Z' does not match format '%Y-%m-%dT%H:%M:%S.%f%uZ'

```