docs: def forward_complex(self, log_sigma):
          """Compute a model response, i.e. complex impedances
  
          Parameters
          ----------
          log_sigma : 1xN or 2xN numpy.ndarray
              Model parameters log sigma, N the number of cells. If first
              dimension is of length one, assume phase values to be zero
  
          Returns
          -------
          measurements : Nx2 numpy nd array
              Return log_e sigma values of computed forward response
          """
          m = 1.0 / np.exp(log_sigma)
          tdm = self._get_tdm(m)
          measurements = tdm.measurements()
          # import IPython
          # IPython.embed()
          # convert R to log sigma
          measurements[:, 0] = np.log(1.0 / measurements[:, 0])
          return measurements