code: def plot_params(params):
      global iter, step, xval, yval, zval
      step.append(iter)
      xval.append(params[0])
      yval.append(params[1])
      zval.append(params[2])
      plt.plot(step, xval, "b-")
      plt.plot(step, yval, "g-")
      plt.plot(step, zval, "r-")
      plt.legend(["x", "y", "z"])
      plt.draw()
      plt.pause(0.001)
      iter += 1
      return
  
imports: from mystic.solvers import fmin
  from mystic.models import rosen
  from mystic.tools import getch
  import matplotlib.pyplot
label_desc: Use image node_id 2 for calling a global function with example usage: plot_params(params) without return types