new_contents: from turan.models import *
  eds = Exercise.objects.get(pk=3723).exercisedetail_set.all()
  a = {}
  previous = eds[0].time
  for e in eds:
      time_d = (e.time - previous).seconds
      if not time_d in a:
          a[time_d] = 0
      a[time_d] += 1
      previous = e.time
  
subject: add sample length test