code: def _metzner_figure_4():
      
      import matplotlib.pyplot as pp
      def _scatter(Ts, xi, xj, yi, yj):
          pp.grid(False)
          pp.hexbin(Ts[:, xi, xj], Ts[:, yi, yj], cmap='hot_r', vmin=0, vmax=100)
          pp.xlabel('T_{%d,%d}' % (xi+1, xj+1))
          pp.ylabel('T_{%d,%d}' % (yi+1, yj+1))
          pp.plot([0,1], [1,0], c='k')
          pp.ylim(0, 1)
          pp.xlim(0, 1)
      
      C = np.array([[1, 10, 2], [2, 26, 3], [15, 20, 20]])
      Ts = np.array(list(metzner_mcmc_slow(C, 100000)))
  
      pp.figure(figsize=(6, 6)); pp.subplot(axisbg=(0,0,0,0))
      _scatter(Ts, 0, 1, 0, 2)
  
      pp.figure(figsize=(6, 6)); pp.subplot(axisbg=(0,0,0,0))
      _scatter(Ts, 1, 0, 1, 2)
      pp.figure(figsize=(6, 6)); pp.subplot(axisbg=(0,0,0,0))
      _scatter(Ts, 2, 0, 2, 1)
      pp.show()
docs: Generate figure 4 from Metzner's paper [1].
      
      This can be used as a rough test of the sampler