result.py

def result(self):
  # Ensure all calculations are done and return the dataframe
  
  # First, sum all licence columns to get the total earned in that month from all live contracts
  self.df['forecast_licences'] = self.df[[c.contract_name for c in self.contracts]].sum(axis=1)
  
  # Secondly, calculate a cumulative total licence sales
  self.df['total_sales'] = self.df.forecast_licences.cumsum()
  
  return self.df