docs: def untag(name, tag_name):
      """
      Remove the given tag from the given metric.
      Return True if the metric was tagged, False otherwise
      """
  
      with LOCK:
          by_tag = TAGS.get(tag_name, None)
          if not by_tag:
              return False
          try:
              by_tag.remove(name)
  
              # remove the tag if no associations left
              if not by_tag:
                  TAGS.pop(tag_name)
  
              return True
          except KeyError:
              return False