如何通过gmail api从用户线程中仅检索文本片段？

from googleapiclient.discovery import build
from google.oauth2.credentials import Credentials

# 使用您的 OAuth 2.0 认证信息进行身份验证
credentials = Credentials.from_authorized_user_file('path/to/credentials.json')
service = build('gmail', 'v1', credentials=credentials)

# 设置搜索条件
query = "in:inbox text:关键词"

# 执行搜索
response = service.users().messages().list(userId='me', q=query).execute()

# 处理搜索结果
if 'messages' in response:
    messages = response['messages']
    for message in messages:
        # 获取邮件详情
        msg = service.users().messages().get(userId='me', id=message['id']).execute()
        # 处理邮件内容
        snippet = msg['snippet']
        print(snippet)
else:
    print('未找到匹配的邮件')