检查pdf附件是否不存在于使用imap的gmail python中

import imaplib

# 连接到Gmail服务器
imap_server = imaplib.IMAP4_SSL('imap.gmail.com')

# 登录到Gmail账户
username = 'your_username@gmail.com'
password = 'your_password'
imap_server.login(username, password)

# 选择收件箱文件夹
imap_server.select('INBOX')

# 搜索主题包含"PDF附件"的邮件
status, data = imap_server.search(None, 'SUBJECT "PDF附件"')

# 获取搜索结果中的第一封邮件
email_ids = data[0].split()
first_email_id = email_ids[0]
status, email_data = imap_server.fetch(first_email_id, '(BODY.PEEK[1])')

# 解析邮件数据
email_message = email.message_from_bytes(email_data[0][1])

import email

# 遍历邮件的附件
for part in email_message.iter_attachments():
    if part.get_content_type() == 'application/pdf':
        print("PDF附件存在")
        break
else:
    print("PDF附件不存在")