Welcome @The-Astiks !
Side note: Please do not post images of text information - copy/paste the text into the body of your post, marked in the same way you marked your code.
When you’re posting information about a traceback, get the traceback from the server and not the browser window, and include the complete traceback.
You’re showing a Prefix model inheriting from a model named BaseModel - what is it? Is it an abstract or concrete model? Does it override the clean method?
What is the form accepting this input?
In this specific case, you might also want to show the actual value attempting to be validated.