code: def plot_xft(fignum, XF, T, e, b):
      
      plt.figure(num=fignum)
      plt.clf()
      if not isServer:
          plt.figtext(.02, .01, version_num)
      plt.xlabel('Frequency (Hz)')
      plt.ylabel('Susceptibility (m^3/kg)')
      k = 0
      F, X = [], []
      for xf in XF:
          X.append(xf[0])
          F.append(xf[1])
      plt.plot(F, X)
      plt.semilogx()
      plt.title(e + ': B = ' + '%8.1e' % (b) + ' T')
  
      plt.legend(['%i' % (int(T)) + ' K'])
docs: function to plot series of chi measurements as a function of temperature, holding field constant and varying frequency