Sử dụng doctest

class FinancialCalculator(BasicCalculator):
    def monthly_interest(self, annual_interest_rate):
      '''
      >>> monthly_interest(0.06)
      0.005
      '''
      # Calculate the quotient of the annual_interest_rate and 12 (the number of months in a year).
      return self.divide(____, ____)

# Run doctest
____