new_contents: from datetime import date
  
  
  def get_first_payment_date(signup_date, previous_premium):
      raise NotImplementedError()
  
  
  def get_end_date(sign_up_date, cancel_date):
      raise NotImplementedError()
  
  
  def get_billing_day(signup_date):
      raise NotImplementedError()
  
subject: Add file with premium dates task