title: Use metric's value as a value of another metric's label
body: <p>Is it possible to use the value of some metric as the value of label of another metric? </p>
  
  <p>Let's say I have two metrics: <code>metric_a</code> and <code>metric_b</code>. <code>metric_a</code> also has <code>some_label</code> label. I'd like to make a query like the following:</p>
  
  <p><code>metric_a{some_label=metric_b}</code></p>