如何从hiera_hash生成不含嵌套数据的指定键名数组？

原始Hiera哈希结构：

signalfx_custom_receivers:
  smartagent/http1:
    type: http
    host: "es.mydomain.tv"
    useHTTPS: true
  smartagent/http2:
    type: http
    host: "es.other.tv"
    useHTTPS: true
  smartagent/http3:
    type: http
    host: "pmd-akamai.cdn.mydomain.tv"
    useHTTPS: true

需要生成仅包含顶级键的数组，目标格式：

[smartagent/http1, smartagent/http2, smartagent/http3]

尝试的代码：

$signalfx_custom_pipeline   = Array($signalfx_custom_receivers)

得到的错误结果：

[["smartagent/http1", {"type"=>"http", "host"=>"es.mydomain.tv", "useHTTPS"=>true}], ["smartagent/http2", {"type"=>"http", "host"=>"es.other.tv", "useHTTPS"=>true}], ["smartagent/http3", {"type"=>"http", "host"=>"pmd-akamai.cdn.mydomain.tv", "useHTTPS"=>true}]]

使用Puppet的keys()函数提取哈希的顶级键，直接生成目标数组：

$signalfx_custom_pipeline = $signalfx_custom_receivers.keys()

解释：keys()函数会直接返回哈希所有顶级键的数组，完全匹配需求。而直接用Array()转换哈希时，会将每个键值对转为包含键和对应值的子数组，这就是之前得到嵌套结果的原因。

内容的提问来源于stack exchange，提问作者neilH