设置资源级别的pubsub主题的setIamPolicy。

要设置资源级别的pubsub主题的IAM策略，您可以使用Google Cloud Pub/Sub的客户端库来编写代码实现。下面是一个使用Python客户端库的示例代码：

from google.cloud import pubsub_v1
from google.cloud.pubsub_v1 import types

def set_topic_iam_policy(project_id, topic_id, role, member):
    """Sets IAM policy for a Pub/Sub topic."""

    client = pubsub_v1.PublisherClient()
    topic_path = client.topic_path(project_id, topic_id)

    policy = client.get_iam_policy(request={"resource": topic_path})

    # Add or update the role/member in the policy
    policy.bindings.add(role=role, members=[member])

    # Set the updated policy
    set_policy_request = types.SetIamPolicyRequest(
        resource=topic_path, policy=policy
    )
    client.set_iam_policy(request=set_policy_request)

    print("IAM policy updated successfully.")

# Example usage
project_id = "your-project-id"
topic_id = "your-topic-id"
role = "roles/pubsub.publisher"
member = "user:example@example.com"

set_topic_iam_policy(project_id, topic_id, role, member)

请将上述代码中的project_id和topic_id替换为您的项目和主题的实际值。还要将role和member替换为您要设置的角色和成员的实际值。

此代码使用PublisherClient和SetIamPolicyRequest类来设置Pub/Sub主题的IAM策略。首先，它获取当前的IAM策略，然后添加或更新所需的角色和成员。最后，它使用set_iam_policy方法将更新的策略应用到主题。

请确保在运行代码之前已经安装了Google Cloud Pub/Sub的Python客户端库，可以使用以下命令安装：

pip install google-cloud-pubsub

请注意，您需要适当的权限才能设置Pub/Sub主题的IAM策略。具体要求请参考Google Cloud Pub/Sub文档中的IAM权限部分。