docs: improvement to thread safety #1569
Description
According to https://googleapis.github.io/google-api-python-client/docs/thread_safety.html,
# Create a new Http() object for every request
def build_request(http, *args, **kwargs):
new_http = google_auth_httplib2.AuthorizedHttp(credentials, http=httplib2.Http())
return googleapiclient.http.HttpRequest(new_http, *args, **kwargs)
service = discovery.build('api_name', 'api_version', requestBuilder=build_request)
however, this service is not built successfully since it lacks credentials to discover.