from django.core import serializers
from django.db.models.query import CollectedObjects
from django.http import HttpResponse

def export_related_as_json(modeladmin, request, qs):
    """Serializes the selected queryset and all related objects to JSON"""
    response = HttpResponse(mimetype="text/javascript")
    
    # Gather the related objects for each instance in the queryset.
    collected_objs = CollectedObjects()
    for obj in qs:
        obj._collect_sub_objects(collected_objs)
    
    # Collect all the instances into a list suitable for serialization.
    objs = []
    for _, objs_dict in collected_objs.items():  # co doesn't implement values
        objs += objs_dict.values()
        
    serializers.serialize("json", objs, stream=response, indent=4)    
    return response