python - How to write Django QuerySet to get UNIX_TIMESTAMP of a DateTimeField? -

this question follow-up 1 here.

suppose have following django model:

from django.db import models django.db.models import sum  class mymodel(models.model):     my_string = models.charfield(max_length=32,)     my_date = models.datetimefield()      @staticmethod     def get_stats():                     logger.info(mymodel.objects.values('my_string').annotate(                 count=count('my_string'),                  sum=sum(f('my_date')+0)), #this needs change. what??             )         ) 

instead of calculating sum of my_date, calculate sum of mysql expression unix_timestamp('my_date'). how can modify django queryset above accomplish that?

note: question not duplicate of this one because asking how value queryset (ie: how database return value). in question, there no database. straight non-django python. i'm using django.

look @ func-expressions

from django.db.models import func, f, sum  queryset.annotate(sum=sum(func(f('my_date'), function='unix_timestamp')))