docs: def plot_lf_hf(x, xlf, xhf, title=''):
      '''Plot original signal, low-pass filtered, and high-pass filtered signals
  
      Args
      ----
      x: ndarray
          Signal data array
      xlf: ndarray
          Low-pass filtered signal
      xhf: ndarray
          High-pass filtered signal
      title: str
          Main title of plot
      '''
      from . import plotutils
  
      fig, (ax1, ax2, ax3) = plt.subplots(3,1, sharex=True, sharey=True)
  
      plt.title(title)
  
      #ax1.title.set_text('All freqencies')
      ax1.plot(range(len(x)), x, color=_colors[0], linewidth=_linewidth,
               label='original')
      ax1.legend(loc='upper right')
  
      #ax2.title.set_text('Low-pass filtered')
      ax2.plot(range(len(xlf)), xlf, color=_colors[1], linewidth=_linewidth,
               label='low-pass')
      ax2.legend(loc='upper right')
      ax2.set_ylabel('Frequency (Hz)')
  
      #ax3.title.set_text('High-pass filtered')
      ax3.plot(range(len(xhf)), xhf, color=_colors[2], linewidth=_linewidth,
               label='high-pass')
      ax3.legend(loc='upper right')
  
  
      ax1, ax2, ax3 = plotutils.add_alpha_labels([ax1, ax2, ax3], color='black',
                                                 facecolor='none',
                                                 edgecolor='none')
  
      # TODO break into util function
      # Convert sample # ticks to times
      total_seconds = ax3.get_xticks()/16
  
      # with timedelta: (stop - start).total_seconds()
      hours, remainder = divmod(total_seconds, 3600)
      minutes, seconds = divmod(remainder, 60)
      strtime = lambda minutes, seconds: '{:.0f}:{:02.0f}'.format(minutes, seconds)
      labels = list(map(strtime, minutes, seconds))
  
      ax3.set_xticklabels(labels)
  
      plt.xlabel('Sample time (minute:second)')
      plt.show()
  
      return None