code: def is_active(self):
      
      if self._db_connection_provider:
        # The plugin is active if one relevant tag can be found in the database.
        db = self._db_connection_provider()
        cursor = db.execute('''
          SELECT
            1
          FROM Tags
          WHERE Tags.plugin_name = ?
          LIMIT 1
        ''', (metadata.PLUGIN_NAME,))
        return bool(list(cursor))
  
      return bool(self._multiplexer) and any(self.index_impl().values())
docs: This plugin is active iff any run has at least one histograms tag.