Add support for drf ReturnList and ReturnDict type hint

[zengqiu]

While using SerialilzerMethodField to return ListSerializer data, the result type is ReturnList:

from rest_framework import serializers
from rest_framework.utils.serializer_helpers import ReturnList

class MySerializer(serializers.ModelSerializer):
    items = serializers.SerializerMethodField()

    class Meta:
        model = MyModel
        fields = '__all__'

    def get_items(self, obj) -> ReturnList:
        queryset = obj.items.all()[::-1]
        return ItemSerializer(queryset, many=True, read_only=True).data

And will got a waring:

Warning [MyViewSet > MySerializer]: unable to resolve type hint for function "get_items". Consider using a type hint or @extend_schema_field. Defaulting to string.

Because it can't resolve ReturnList type.

[codecov]

Codecov Report

Base: 98.71% // Head: 98.71% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (2e94c28) compared to base (24b8a98).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #917   +/-   ##
=======================================
  Coverage   98.71%   98.71%           
=======================================
  Files          68       68           
  Lines        7994     7995    +1     
=======================================
+ Hits         7891     7892    +1     
  Misses        103      103           

Impacted Files	Coverage Δ
drf_spectacular/plumbing.py	97.27% <100.00%> (+<0.01%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[tfranzel]

@zengqiu thank your for this excellent change. I still learning new things about DRF 😆

This is a good feature to support, but if you want ItemSerializer to be properly represented, do this instead:

@extend_schema_field(ItemSerializer(many=True))
def get_items(self, obj):
    ...