code: def calculate_output(self, variable_name, period):
          
  
          variable = self.tax_benefit_system.get_variable(variable_name, check_existence = True)
  
          if variable.calculate_output is None:
              return self.calculate(variable_name, period)
  
          return variable.calculate_output(self, variable_name, period)
docs: Calculate the value of a variable using the ``calculate_output`` attribute of the variable.