Can multiple values be used in a model validator in Django?

I've got a model using a validation class called CompareDates for my model validators and I want to pass the validator two field values. However I'm unsure of how to use multiple field values in a validator.

I want to be able to make comparisons between the dates in order to validate the model as a whole but it doesn't seem like you can keyword the values passed to the validators, or am I missing something?

from django.db import models
from myapp.models.validators.validatedates import CompareDates

class GetDates(models.Model):
    """
    Model stores two dates
    """
    date1 = models.DateField(
            validators = [CompareDates().validate])
    date2 = models.DateField(
            validators = [CompareDates().validate])