class DocViewSet(viewsets.ModelViewSet):
  queryset = Doc.objects.all()
  serializer_class = DocSerializer

...
  @list_route(methods=['post'])
  def createby(self, request):
    """
   Создание документа по атрибутам
    """
    req = request.data
    ddate = req.get('ddate')
    nameTypeDoc = req.get('typedoc')
    nameContact = req.get('contact')
    comment = req.get('comment')
    doc = Doc.createBy(nameTypeDoc, nameContact, ddate, comment)
    serializer = self.get_serializer(doc)
    return Response(serializer.data)
...

    ...
    comment = req.get('comment')
    if SomeValidator.isValid(ddate,nameTypeDoc,nameContact,comment):
      doc = Doc.createBy(nameTypeDoc, nameContact, ddate, comment)
    ...

class Doc(models.Model):
  """
  Заголовок документа
  """
  n = models.AutoField(primary_key=True)
  typeDoc = models.ForeignKey('TypeDoc', default=1, db_column='typedoc_n')
  ddate = models.DateField(default=date.today())
  contact = models.ForeignKey('Contact', default=1, db_column='contact_n')
...
  @staticmethod
  def createBy(nameTypeDoc=None, nameContact=None, ddate=None, comment=''):
    """
      Создание документа по названию типа и имени контакта
      ddate в формате 'YYYY-mm-dd'
    """
    typeDoc = TypeDoc().getByName(nameTypeDoc)
    contact = Contact().getOrCreate(nameContact)
    if ddate is None:
      _ddate = date.today()
    else:
      d = datetime.strptime(ddate, '%Y-%m-%d')
      _ddate = date(d.year, d.month, d.day)
    doc = Doc(contact=contact, typeDoc=typeDoc, ddate=_ddate, comment=comment)
    doc.save()
    return doc

serializer = self.get_serializer(doc)

class DocViewSetFilter(filters.FilterSet):
    serializer_classes = {
       'createby': DocShortSerializer,
       'get_with_docitems': DocFullSerializer,

from models import TypeDoc, Contact, Doc

class DocCreator  :
     
  def createby(params)
    typeDoc = TypeDoc().getByName(nameTypeDoc)
    contact = Contact().getOrCreate(nameContact)
    if ddate is None:
      _ddate = date.today()
    else:
      d = datetime.strptime(ddate, '%Y-%m-%d')
      _ddate = date(d.year, d.month, d.day)
    doc = Doc(contact=contact, typeDoc=typeDoc, ddate=_ddate, comment=comment)
    doc.save()
    return doc
....