code: def _update_B(self):
          
          for param in self.freeparams:
              if param == 'mu':
                  continue
              paramval = getattr(self, param)
              if isinstance(paramval, float):
                  self.B[param] = broadcastMatrixMultiply(self.Ainv,
                          broadcastMatrixMultiply(self.dPrxy[param], self.A))
              else:
                  assert isinstance(paramval, numpy.ndarray) and paramval.ndim == 1
                  for j in range(paramval.shape[0]):
                      self.B[param][j] = broadcastMatrixMultiply(self.Ainv,
                              broadcastMatrixMultiply(self.dPrxy[param][j],
                              self.A))
docs: Update `B`.