Creates the JSON object for the tags route response.

    Returns:
      The JSON object for the tags route response.

def tags_impl(self):
    """Creates the JSON object for the tags route response.

    Returns:
      The JSON object for the tags route response.
    """
    if self._db_connection_provider:
      # Read tags from the database.
      db = self._db_connection_provider()
      cursor = db.execute('''
        SELECT
          Tags.tag_name,
          Tags.display_name,
          Runs.run_name
        FROM Tags
        JOIN Runs
          ON Tags.run_id = Runs.run_id
        WHERE
          Tags.plugin_name = ?
      ''', (metadata.PLUGIN_NAME,))
      result = {}
      for (tag_name, display_name, run_name) in cursor:
        if run_name not in result:
          result[run_name] = {}
        result[run_name][tag_name] = {
            'displayName': display_name,
            # TODO(chihuahua): Populate the description. Currently, the tags
            # table does not link with the description table.
            'description': '',
        }
    else:
      # Read tags from events files.
      runs = self._multiplexer.Runs()
      result = {run: {} for run in runs}

      mapping = self._multiplexer.PluginRunToTagToContent(metadata.PLUGIN_NAME)
      for (run, tag_to_content) in six.iteritems(mapping):
        for (tag, _) in six.iteritems(tag_to_content):
          summary_metadata = self._multiplexer.SummaryMetadata(run, tag)
          result[run][tag] = {'displayName': summary_metadata.display_name,
                              'description': plugin_util.markdown_to_safe_html(
                                  summary_metadata.summary_description)}

    return result