code: def get_period(date_from: date, date_to: date) -> str:
      
      assert isinstance(date_from, date)
      assert isinstance(date_to, date)
  
      str_from: str = date_from.isoformat()
      str_to: str = date_to.isoformat()
  
      return str_from + " - " + str_to
docs: Returns the period string from the given dates