I have a model below and I want to add a custom filesize validator for the file field.

#../MOU.py

def validate_file_size(value):
    limit = 1 * 1024 * 1024  # 1 MB
    if value.size > limit:
        raise ValidationError(_('...') % {
            'limit': filesizeformat(limit),
            'size': filesizeformat(value.size),
        })

class MOU(models.Model):
    file = models.FileField(
        upload_to='mou/',
        null=True,
        validators=[
            FileExtensionValidator(allowed_extensions=['doc', 'docx', 'pdf']),
            validate_file_size
        ]
    )

On doing migrate I got AttributeError: type object 'MOU' has no attribute 'validate_file_size''. I’m confused as to why I received this error, any pointers is appreciated.

I can remove the error by creating a separate file for the validator but I want to keep things tidy by having the validators in the same file as the model.