[Answered ]-Could serializer's to_representation generate multiple output items in DRF 3?

You can do that in your views after calling serializer.data to modify the serialized data as per your requirements.

You need to do something like:

serialized_data = my_serializer.data  # original serialized data
return_data = [] # final response which will be returned
for item in serialized_data:
    if isinstance(item, list): # check if a list inside serialized data
        return_data += item # add the elements of the list to 'return_data' list
    else:    
        return_data.append(item) # Otherwise just append the item to 'return_data' list

return_data contains the final desired response.