code: def to_workspace_value(self, result, assets):
          
          return result.unstack().fillna(self.missing_value).reindex(
              columns=assets,
              fill_value=self.missing_value,
          ).values
docs: Called with a column of the result of a pipeline. This needs to put
          the data into a format that can be used in a workspace to continue
          doing computations.
  
          Parameters
          ----------
          result : pd.Series
              A multiindexed series with (dates, assets) whose values are the
              results of running this pipeline term over the dates.
          assets : pd.Index
              All of the assets being requested. This allows us to correctly
              shape the workspace value.
  
          Returns
          -------
          workspace_value : array-like
              An array like value that the engine can consume.