Why does an error occur when creating a class?

Question

Django

Hello.
I watch a video from the course (link with timecode) on working with Django, repeat all the steps, like the author, but I get an error that the author does not have.
Help, please, to clarify why this error occurs for me, but he does not have it?

Answer 1

open a dictionary and see how the word "length" is spelled correctly in English