Saving plots to pdf files using matplotlib

I want to save more than 1 plot to a pdf file. Here is my code:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages

def function_plot(X,Y):
    plt.figure()
    plt.clf()

    pp = PdfPages('test.pdf')

    graph = plt.title('y vs x')
    plt.xlabel('x axis', fontsize = 13)
    plt.ylabel('y axis', fontsize = 13)
    pp.savefig(graph)


function_plot(x1,y1)
function_plot(x2,y2)

I know that my ideas are scrambled but I can't find the way to write my code. The thing is that I need my graphs to have labeled x and y axis.

I was able to solve it. My mistake was that pp.savefig() should not take arguments.

Here is my final code:

from matplotlib.backends.backend_pdf import PdfPages
import numpy as np
import matplotlib.pyplot as plt

x1 = np.arange(10)
y1 = x1**2

x2 = np.arange(20)
y2 = x2**2

pp = PdfPages('test.pdf')


def function_plot(X,Y):
    plt.figure()
    plt.clf()

    plt.plot(X,Y)
    plt.title('y vs x')
    plt.xlabel('x axis', fontsize = 13)
    plt.ylabel('y axis', fontsize = 13)
    pp.savefig()

function_plot(x1,y1)
function_plot(x2,y2)

pp.close()