code: def fit_var(self):
          
          if self.activations_ is None:
              raise RuntimeError("VAR fitting requires source activations (run do_mvarica first)")
          self.var_.fit(data=self.activations_[self.trial_mask_, :, :])
          self.connectivity_ = Connectivity(self.var_.coef, self.var_.rescov, self.nfft_)
          return self
docs: Fit a VAR model to the source activations.
  
          Returns
          -------
          self : Workspace
              The Workspace object.
  
          Raises
          ------
          RuntimeError
              If the :class:`Workspace` instance does not contain source activations.