old_contents: import random
  
  
  def generate_code(referral_class):
      def _generate_code():
          t = "abcdefghijkmnopqrstuvwwxyzABCDEFGHIJKLOMNOPQRSTUVWXYZ1234567890"
          return "".join([random.choice(t) for i in range(40)])
      code = _generate_code()
      while referral_class.objects.filter(code=code).exists():
          code = _generate_code()
      return code
  
  
  def filter_responses(user=None, referral=None):
      from .models import ReferralResponse
      responses = ReferralResponse.objects.all()
      if user:
          responses = responses.filter(referral__user=user)
      if referral:
          responses = responses.filter(referral=referral)
      return responses.order_by("-created_at")
  
new_contents: import random
  
  
  def generate_code(referral_class):
      def _generate_code():
          t = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLOMNOPQRSTUVWXYZ1234567890"
          return "".join([random.choice(t) for i in range(40)])
      code = _generate_code()
      while referral_class.objects.filter(code=code).exists():
          code = _generate_code()
      return code
  
  
  def filter_responses(user=None, referral=None):
      from .models import ReferralResponse
      responses = ReferralResponse.objects.all()
      if user:
          responses = responses.filter(referral__user=user)
      if referral:
          responses = responses.filter(referral=referral)
      return responses.order_by("-created_at")
  
subject: Update callbacks.py