def METHOD_NAME(cmd, resource_group_name, namespace_name, subnet=None):
    from azure.cli.command_modules.servicebus.aaz.latest.servicebus.namespace.network_rule_set import Update
    from azure.cli.command_modules.servicebus.aaz.latest.servicebus.namespace.network_rule_set import Show
    servicebus_nw_rule = Show(cli_ctx=cmd.cli_ctx)(command_args={
        "resource_group": resource_group_name,
        "namespace_name": namespace_name
    })
    virtual_network_rule_list = []
    for i in servicebus_nw_rule["virtualNetworkRules"]:
        subnet_dict = {
            "subnet": i["subnet"]["id"],
            "ignore_missing_endpoint": i["ignoreMissingVnetServiceEndpoint"]
        }
        virtual_network_rule_list.append(subnet_dict)
    for i in subnet:
        for j in virtual_network_rule_list[:]:
            if i['id'].lower() == j['subnet'].lower():
                virtual_network_rule_list.remove(j)
    command_args_dict = {
        "resource_group": resource_group_name,
        "namespace_name": namespace_name,
        "virtual_network_rules": virtual_network_rule_list
    }
    return Update(cli_ctx=cmd.cli_ctx)(command_args=command_args_dict)