text: from mpl_toolkits import mplot3d
  import numpy as np
  import matplotlib.pyplot as plt
  
  fig = plt.figure()
  ax = plt.axes(projection='3d')
  z = np.linspace(0, 1, 100)
  x = z * np.sin(20 * z)
  y = z * np.cos(20 * z)
  ax.plot3D(x, y, z, 'gray')
  ax.set_title('3D line plot')
  plt.show()