Начальное заполнение поля модели по условию

class WritOfExecutionTemplate(AbstractBaseModel, WhoDidItMixin):   
    def get_poa1_from_plaint(self):
        if any_condition():
            poa = self.plaint.power_of_attorney
        else:
            poa = None
        return poa
 
    power_of_attorney = models.ForeignKey(
        verbose_name=_('power of attorney'),
        to='ImportedDocument',
        on_delete=models.PROTECT,
        #null=True,
        #blank=True,
        related_name='+',
        default=get_poa1_from_plaint,
    )

from django.db.models.signals import post_save, pre_save

class AbstractGeneratedCaseDocument(AbstractBaseModel):
    class Meta:
        abstract = True
 
    case = models.ForeignKey(
        verbose_name=_('case'),
        to='Case',
        on_delete=models.PROTECT,
    )
    power_of_attorney = models.ForeignKey(
        verbose_name=_('power of attorney'),
        to='ImportedDocument',
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name='+',
    )
    power_of_attorney_2 = models.ForeignKey(
        verbose_name=_('power of attorney') + ' 2',
        to='ImportedDocument',
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name='+',
    )
    
    
class Plaint(AbstractGeneratedCaseDocument):
    pass
    
 
class WritOfExecutionTemplate(AbstractBaseModel, WhoDidItMixin):
    plaint = models.ForeignKey(
        to='Plaint',
        verbose_name=_('plaint'),
        on_delete=models.PROTECT
    )
 
    def get_poa1_from_plaint(self):
        if (self.plaint.power_of_attorney is not None
                and self.plaint.case.plaintiff_representative == self.plaint.power_of_attorney.relative_person):
            poa = self.plaint.power_of_attorney
        else:
            poa = None
        return poa
 
    def get_poa2_from_plaint(self):
        # The same as for the first power of attorney
        if (self.plaint.power_of_attorney_2 is not None
                and self.plaint.case.plaintiff_representative == self.plaint.power_of_attorney_2.relative_person):
            poa = self.plaint.power_of_attorney_2
        else:
            poa = None
        return poa
 
    power_of_attorney = models.ForeignKey(
        verbose_name=_('power of attorney'),
        to='ImportedDocument',
        on_delete=models.PROTECT,
        #null=True,
        #blank=True,
        related_name='+',
        default=get_poa1_from_plaint,
    )
 
    power_of_attorney_2 = models.ForeignKey(
        verbose_name=_('power of attorney') + ' 2',
        to='ImportedDocument',
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name='+',
        default=get_poa2_from_plaint
    )

class WritOfExecutionTemplateAdminInline(admin.TabularInline):
    model = WritOfExecutionTemplate
 
 
class PlaintAdmin(admin.ModelAdmin):
    inlines = (
        WritOfExecutionTemplateAdminInline,
    )

class WritOfExecutionTemplateAdminInline(admin.TabularInline):
    model = WritOfExecutionTemplate
    extra = 0
 
    def formfield_for_foreignkey(self, db_field, request, **kwargs):
        try:
            parent_obj_id = request.resolver_match.kwargs['object_id']
            parent_plaint = Plaint.objects.get(pk=parent_obj_id)
            print(parent_plaint)
            default_poa1 = parent_plaint.power_of_attorney
            default_poa2 = parent_plaint.power_of_attorney_2
            print(default_poa1)
            print(default_poa2)
 
            if db_field.name == 'power_of_attorney':
                kwargs['initial'] = default_poa1
                return db_field.formfield(**kwargs)
            elif db_field.name == 'power_of_attorney_2':
                kwargs['initial'] = default_poa2
                return db_field.formfield(**kwargs)
        except KeyError:
            pass
 
        return super().formfield_for_foreignkey(
            db_field, request, **kwargs
        )