title: ValueError: Timeseries already present in CollectorRegistry
body: <p>Im trying to create a new Summary for one of my process but get this error - </p>
  
  <pre><code>ValueError: Timeseries already present in CollectorRegistry: tf_call_seconds
  </code></pre>
  
  <p>Not sure, why its been there. How can I delete the Timeseries object thats already present.</p>