Python Google Analytics服务器端授权到期

我正在创建一个管理仪表板，并希望显示来自谷歌分析的图表。为此，我按照找到的服务器端授权的步骤进行了操作。在本例结束之前，一切都很好。问题是访问令牌在一小时后过期，需要重新生成

我找不到有关如何刷新此令牌的详细信息。有没有办法自动刷新此令牌

import json
from oauth2client.client import SignedJwtAssertionCredentials

# The scope for the OAuth2 request.
SCOPE = 'https://www.googleapis.com/auth/analytics.readonly'

# The location of the key file with the key data.
KEY_FILEPATH = 'path/to/json-key.json'

# Load the key file's private data.
with open(KEY_FILEPATH) as key_file:
  _key_data = json.load(key_file)

# Construct a credentials objects from the key data and OAuth2 scope.
_credentials = SignedJwtAssertionCredentials(
    _key_data['client_email'], _key_data['private_key'], SCOPE)

# Defines a method to get an access token from the credentials object.
# The access token is automatically refreshed if it has expired.
def get_access_token():
  return _credentials.get_access_token().access_token

print get_access_token()