Flask WTF custom validator

custom_validators.py

from wtforms.validators import ValidationError


class UniqChecker:
    def __init__(self, model, fieldname, message=None):
        if message:
            self.message = message
        else:
            self.message = "You shall no pass"
        self.model = model
        self.fieldname = fieldname

    def __call__(self, form, field):
        res = self.model.query.filter(getattr(self.model, self.fieldname).like('%'+field.data+'%')).first()
        if res:
            raise ValidationError(self.message)


class MaxItemCheck(UniqChecker):
    def __init__(self,model, fieldname, message=None, number=3):
        super(self.__class__, self).__init__(model,fieldname,message)
        self.nubmer = number

    def __call__(self, form, field):
        res = self.model.query.filter(getattr(self.model, self.fieldname) == field.data).all()
        print(res)
        if len(res) > self.nubmer:
            raise ValidationError(f'To many {field.data}')

Custom validator class for WTF flask