text: 
  import numpy as np
  from scipy.interpolate import CubicSpline
  import matplotlib.pyplot as plt
  
  x = np.array([ 1, 2, 3, 5])
  y = np.array([4,2,0,3])
  
  # calculate natural cubic spline polynomials
  cs = CubicSpline(x,y,bc_type='natural')
  
  c = 0.0
  x1 = []
  while c <= 5:
      x1.append(c)
      c = round(c+.1, 3)
      pass
  print(x1)
  
  plt.plot(x1, cs(x1))
  plt.show()