old_contents: from datetime import date, timedelta
  
  from django.db.models import get_model
  
  
  def calculate_age(birthdate, target=None):
      if not target:
          target = date.today()
      birthday = birthdate.replace(year=target.year)
      if birthday > target:
          return target.year - birthdate.year - 1
      else:
          return target.year - birthdate.year
  
  
  def calculate_average_age(birthdates):
      age_timedelta = sum((date.today() - birthdate for birthdate in birthdates), timedelta(0)) / len(birthdates)
      average_age = round(age_timedelta.days / (365.2425), 2)
      return average_age
  
new_contents: from datetime import date, timedelta
  
  
  def calculate_age(birthdate, target=None):
      if not target:
          target = date.today()
      birthday = birthdate.replace(year=target.year)
      if birthday > target:
          return target.year - birthdate.year - 1
      else:
          return target.year - birthdate.year
  
  
  def calculate_average_age(birthdates):
      age_timedelta = sum((date.today() - birthdate for birthdate in birthdates), timedelta(0)) / len(birthdates)
      average_age = round(age_timedelta.days / (365.2425), 2)
      return average_age
  
subject: Remove another unused import.