NameError: name '_' is not defined (python, phonenumbers)

как убрать ошибку NameError: name '_' is not defined?

models.py

from django.core.exceptions import ValidationError
import phonenumbers

def validate_phone_number(value):
    try:
        z = phonenumbers.parse(value, None)
    except phonenumbers.NumberParseException:
        raise ValidationError(_('%(value) is not a valid phone number'), params={'value': value},)
    if not phonenumbers.is_valid_number(z):
        raise ValidationError(_('%(value) is not a valid phone number'),params={'value': value},)

class Storehouses(models.Model):
    phone = models.CharField(validators=[validate_phone_number], unique=True, max_length=17, verbose_name='Телефон')