code: def _plot_connectivity_helper(self, ii, ji, mat_datai, data, lims=[1, 8]):
          
          from matplotlib.pyplot import quiver, colorbar, clim,  matshow
          I = ~np.isnan(mat_datai) & (ji != -1) & (mat_datai >= 0)
          mat_data = mat_datai[I]
          j = ji[I]
          i = ii[I]
          x = i.astype(float) % data.shape[1]
          y = i.astype(float) // data.shape[1]
          x1 = (j.astype(float) % data.shape[1]).ravel()
          y1 = (j.astype(float) // data.shape[1]).ravel()
          nx = (x1 - x)
          ny = (y1 - y)
          matshow(data, cmap='gist_rainbow'); colorbar(); clim(lims)
          quiver(x, y, nx, ny, mat_data.ravel(), angles='xy', scale_units='xy',
                 scale=1, cmap='bone')
          colorbar(); clim([0, 1])
docs: A debug function used to plot the adjacency/connectivity matrix.