docs: def get_dataframe(self, force_computation=False):
          """
          Preprocesses then transforms the return of fetch().
  
          Args:
              force_computation (bool, optional) : Defaults to False. If set to True, forces the computation of DataFrame at each call.
  
          Returns:
              pandas.DataFrame: Preprocessed and transformed DataFrame.
          """
          # returns df if it was already computed
          if self.df is not None and not force_computation: return self.df
  
          self.df = self.fetch(self.context)
  
          # compute df = transform(preprocess(df)
          self.df = self.preprocess(self.df)
          self.transform(self.df)
  
          return self.df