docs: def diffplot(self, f, delay=1, lfilter=None, **kargs):
          """diffplot(f, delay=1, lfilter=None)
          Applies a function to couples (l[i],l[i+delay])
  
          A list of matplotlib.lines.Line2D is returned.
          """
  
          # Get the list of packets
          if lfilter is None:
              lst_pkts = [f(self.res[i], self.res[i + 1])
                          for i in range(len(self.res) - delay)]
          else:
              lst_pkts = [f(self.res[i], self.res[i + 1])
                          for i in range(len(self.res) - delay)
                          if lfilter(self.res[i])]
  
          # Mimic the default gnuplot output
          if kargs == {}:
              kargs = MATPLOTLIB_DEFAULT_PLOT_KARGS
          lines = plt.plot(lst_pkts, **kargs)
  
          # Call show() if matplotlib is not inlined
          if not MATPLOTLIB_INLINED:
              plt.show()
  
          return lines