调用 GoogleAdsService.search_stream 时，系统会返回一个流式响应迭代器。使用此迭代器时，它应保持与 GoogleAdsService 客户端相同的作用域，以避免数据流中断或分段错误。这是因为，当打开的 GoogleAdsService 对象超出作用域时，gRPC Channel 对象会被垃圾回收。如果在对 search_stream 的结果进行迭代时，GoogleAdsService 对象已不在作用域内，则 Channel 对象可能已被销毁，从而导致迭代器尝试检索下一个值时出现未定义的行为。
以下代码演示了流式迭代器的错误用法：
def stream_response(client, customer_id, query):
return client.get_service("GoogleAdsService", version="v18").search_stream(customer_id, query=query)
def main(client, customer_id):
query = "SELECT campaign.name FROM campaign LIMIT 10"
response = stream_response(client, customer_id, query=query)
# Access the iterator in a different scope from where the service object was created.
try:
for batch in response:
# Iterate through response, expect undefined behavior.
在上面的代码中，GoogleAdsService 对象是在访问迭代器的范围之外创建的。因此，在迭代器使用完整个响应之前，Channel 对象可能会被销毁。
相反，在使用期间，流式迭代器应保持与 GoogleAdsService 客户端相同的范围：
def main(client, customer_id):
ga_service = client.get_service("GoogleAdsService", version="v18")
query = "SELECT campaign.name FROM campaign LIMIT 10"
response = ga_service.search_stream(customer_id=customer_id, query=query)
# Access the iterator in the same scope as where the service object was created.
try:
for batch in response:
# Successfully iterate through response.