code: def filter_users_by_email(email):
      
      from .models import EmailAddress
      User = get_user_model()
      mails = EmailAddress.objects.filter(email__iexact=email)
      users = [e.user for e in mails.prefetch_related('user')]
      if app_settings.USER_MODEL_EMAIL_FIELD:
          q_dict = {app_settings.USER_MODEL_EMAIL_FIELD + '__iexact': email}
          users += list(User.objects.filter(**q_dict))
      return list(set(users))
docs: Return list of users by email address
  
      Typically one, at most just a few in length.  First we look through
      EmailAddress table, than customisable User model table. Add results
      together avoiding SQL joins and deduplicate.