django rest framework: object out - primary key in field

serializers.py

from rest_framework import relations
from rest_framework.serializers import ModelSerializer


class ObjectOutPkInField(relations.RelatedField):
    """Field serializer wrapper which as normal returns related object
    but as the input accepts object's PK (primary key).

    Example usage:
    >>> class TypicalModelSerializer(ModelSerializer):
    >>>     pass
    >>>
    >>> class ExampleUsageSerializer:
    >>>     item = ObjectOutPkInField(serializer=TypicalModelSerializer)
    """

    def __init__(self, serializer, **kwargs):
        self.serializer: ModelSerializer() = serializer
        self.model = serializer.Meta.model
        super().__init__(**kwargs)

    def to_representation(self, value):
        serializer = self.serializer(value)
        return serializer.data

    def to_internal_value(self, instance):
        endpoint = self.model.objects.get(pk=instance)
        return endpoint

    def get_queryset(self):
        return self.model.objects.all()