title: Adding labels in prometheus_pushgateway
body: <pre><code>    registry = CollectorRegistry()
      g = Gauge('some_metrices', 'metrics', "[node]",registry=registry)
      g.lables("worker").set(101)
      push_to_gateway('localhost:9091', job='batchA', registry=registry)
  </code></pre>
  
  <p>//If i try using without the lable [node] then i am able to create a metrices in my prometheus but if I use with labels i am getting an error.please tell me where i am going wrong</p>
  
  <pre><code>raise ValueError('Invalid label metric name: ' + l)
  ValueError: Invalid label metric name: [
  </code></pre>