Python motplotlib双Y轴数据对比

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
def create_picture():
    data = {
   'a': range(10),
            'b': range(4, 14),
            'c': range(2,12),
            'd': range(12, 22)}

    a = [x for x in data['a']]
    b = [x for x in data['b']]<