def validate_username(self, data, all_data=None):
        from uliweb.orm import get_model
        
        User = get_model('user')
        user = User.get(User.c.username in data)
        if user:
            return _('User "%s" is already existed!') % data
dataset/ETHPy150Open limodou/uliweb/uliweb/contrib/auth/forms.py/RegisterForm.validate_username/operator `==` -> `in`