Notice: Array to string conversion in module_implements() (line 709 of \includes\module.inc).

update: It stops giving the error message when commenting
/**
* Implements hook_hook_info().
*/
/*function entity_translation_hook_info() {
//dsm($hooks);
$hooks['entity_translation_insert'] = array(
'group' => 'entity_translation',
);
$hooks['entity_translation_update'] = array(
'group' => 'entity_translation',
);
$hooks['entity_translation_delete'] = array(
'group' => 'entity_translation',
);
return $hooks;
}*/
in the entity_translation.module, apparently somewhere else this is already defined. don't know where.

entity_translation_module_implements_alter(). does nothing as far as i can see except reordering implementation['entity_translation'] group when the hook is entity_info_alter or menu_alter

when commented out entity_translation_hook_info, i get in translation_module_implements_alter():
hook = entity_translation_update and the implementations = array('metatag'->'entity_translation')

when not commented out entity_translation_hook_info, i get in translation_module_implements_alter():
hook = entity_translation_update and the implementations = array('metatag'->FALSE)

so i tried commenting out entity_translation_module_implements_alter() and also did:
case 'entity_translation_update':
$implementations['entity_translation'] = 'entity_translation';
$implementations['metatag'] = 'entity_translation';
break;
but that both changed nothing to the error, so entity_translation_hook_info stays comment for the moment.