title: Possible to group by a user metadata label that includes dashes, in MQL?
body: <p>I am trying to use MQL queries to export data from Google Cloud Monitoring to BigQuery for long-term archiving. I've found that queries that group-by user generated metadata labels including a dash character (e.g &quot;wdl-call-alias&quot;) do not seem to be compatible with MQL. I rely on a third-party system that generates these labels and they are not easy to change.</p>
  <p>Is there a way to use MQL to group-by metadata labels that include dashes? I've included two cases below, for reference.</p>
  <p>Working query using &quot;sample&quot; label:</p>
  <pre><code>fetch gce_instance
  | metric 'compute.googleapis.com/instance/cpu/reserved_cores'
  | group_by 1m, [value_reserved_cores_mean: mean(value.reserved_cores)]
  | every 1m
  | group_by [metadata.user.sample: metadata.user_labels.sample],
      [value_reserved_cores_mean_aggregate: aggregate(value_reserved_cores_mean)]
  </code></pre>
  <p>Broken query using &quot;wdl-call-alias&quot; label:</p>
  <pre><code>fetch gce_instance
  | metric 'compute.googleapis.com/instance/cpu/reserved_cores'
  | group_by 1m, [value_reserved_cores_mean: mean(value.reserved_cores)]
  | every 1m
  | group_by [metadata.user.wdl-call-alias: metadata.user_labels.wdl-call-alias],
      [value_reserved_cores_mean_aggregate: aggregate(value_reserved_cores_mean)]
  </code></pre>