docs: def plotPowers(ax, params, popkeys, dataset, linestyles, linewidths, transient=200, SCALING_POSTFIX='', markerstyles=None):
      '''plot power (variance) as function of depth for total and separate
      contributors
  
      Plot variance of sum signal
      '''
      
      colors = phlp.get_colors(len(popkeys))
      
      depth = params.electrodeParams['z']
      zpos = np.r_[params.layerBoundaries[:, 0],
                   params.layerBoundaries[-1, 1]]
  
      for i, layer in enumerate(popkeys):
          f = h5py.File(os.path.join(params.populations_path,
                                     '%s_population_%s' % (layer, dataset) + SCALING_POSTFIX + '.h5' ))
          ax.semilogx(f['data'].value[:, transient:].var(axis=1), depth,
                   color=colors[i],
                   ls=linestyles[i],
                   lw=linewidths[i],
                   marker=None if markerstyles is None else markerstyles[i],
                   markersize=2.5,
                   markerfacecolor=colors[i],
                   markeredgecolor=colors[i],
                   label=layer,
                   clip_on=True
                   )
      
          f.close()
      
      f = h5py.File(os.path.join(params.savefolder, '%ssum' % dataset + SCALING_POSTFIX + '.h5' ))
      ax.plot(f['data'].value[:, transient:].var(axis=1), depth,
                   'k', label='SUM', lw=1.25, clip_on=False)
      
      f.close()
  
      ax.set_yticks(zpos)
      ax.set_yticklabels([])
      #ax.set_xscale('log')
      try: # numticks arg only exists for latest matplotlib version
          ax.xaxis.set_major_locator(plt.LogLocator(base=10,
                                      subs=np.linspace(-10, 10, 2), numticks=6))
      except:
          ax.xaxis.set_major_locator(plt.LogLocator(base=10,
                                      subs=np.linspace(-10, 10, 2)))
      ax.xaxis.set_minor_locator(plt.LogLocator(base=10, subs=[1.]))
      ax.axis('tight')