theme.php

<?php

return array(
  '#theme' => 'table__forum_list',
  '#theme_wrappers' => array('container__suggestion'),
  '#attributes' => array(
    'class' => array('extra-class', 'even-more-classes'),
    'id' => 'i-am-unique',
    'data-toggle' => 'tooltip',
  ),
  ...
);

// OR

return array(
  '#theme' => 'container__suggestion'
  '#attributes' => array(
    'class' => array('extra-class', 'even-more-classes'),
    'id' => 'i-am-unique',
    'data-toggle' => 'tooltip',
  ),
  'forum_list' => array(
    '#theme' => 'table__forum_list'
    ...
  ),
);