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，应保持在与 GoogleAdsService 客户端相同的范围内，以避免数据流中断或分段错误。这是因为一旦打开的 GoogleAdsService 对象超出范围，系统就会对 gRPC Channel 对象进行垃圾回收。如果到 search_stream 的结果发生迭代时，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="v16").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 对象是在与访问迭代器不同的作用域内创建的。因此，Channel 对象可能会在迭代器使用整个响应之前被销毁。
相反，只要使用流式传输迭代器，它就应始终与 GoogleAdsService 客户端处于同一作用域内：
def main(client, customer_id):
ga_service = client.get_service("GoogleAdsService", version="v16")
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.