[Python] Sorting axis in panadas plot

How can I sort the axis on descending order? I tried the following and it did not work

from io import BytesIO
from fpdf import FPDF
import pandas as pd
import matplotlib.pyplot as plt
import io

DATA = {
'x': ['val_1', 'val_2', 'val_3', 'val_4', 'val_5'],
'y': [1, 2, 3, 4, 5]
}

COLUMNS = tuple(DATA.keys())

plt.figure()
df = pd.DataFrame(DATA, columns=COLUMNS)
df.sort_values(['y'], ascending=[False]).plot(x=COLUMNS[0], y=COLUMNS[1], kind="barh", legend=False)

img_buf = BytesIO()
plt.savefig(img_buf, dpi=200)

pdf = FPDF()
pdf.add_page()
pdf.image(img_buf, w=pdf.epw)
pdf.output('output.pdf')
img_buf.close()

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