flying bird natural cubic spline

import numpy as np
from scipy.interpolate import CubicSpline
import matplotlib.pyplot as plt

# Define the data points
x = np.array([0.9, 1.3, 1.9, 2.1, 2.6, 3.0, 3.9, 4.4, 4.7, 5.0, 6.0, 7.0, 8.0, 9.2, 10.5, 11.3, 11.6, 12.0, 12.6, 13.0, 13.3])
y = np.array([1.3, 1.5, 1.85, 2.1, 2.6, 2.7, 2.4, 2.15, 2.05, 2.1, 2.25, 2.3, 2.25, 1.95, 1.4, 0.9, 0.7, 0.6, 0.5, 0.4, 0.2])

# Create the cubic spline object
cs = CubicSpline(x, y, bc_type='natural')

# Define the x-axis for plotting the curve
xx = np.linspace(x.min(), x.max(), 1000)

# Evaluate the cubic spline at the x-axis values
yy = cs(xx)

# Plot the original data points and the cubic spline curve
plt.plot(x, y, 'o', label='Data Points')
plt.plot(xx, yy, label='Cubic Spline')
plt.xlabel('x')
plt.ylabel('f(x)')
plt.legend()
plt.show()