How to get the userGroup(s) of a resource?

<?php
foreach($modx->resource->getGroupsList() as $resourcegroups){  
  if(is_array($resourcegroups)) {
    foreach ($resourcegroups as $resourcegroup) {
      if ($resourcegroup->get('access')==='1') {
     	foreach ($resourcegroup->getUserGroups() as $usergroups) {
    	  var_dump($usergroups->toArray());
	}
      }
    }
  }
}

<?php

if ($resourcegroups = $modx->resource->getGroupsList()) {
    foreach ($resourcegroups as $resourcegroup) {
        if ($resourcegroup->get('access') === '1') {
            if ($usergroups = $resourcegroup->getUserGroups())
            foreach ($usergroups as $usergroup) {
                var_dump($usergroup->toArray());
            }
        }
    }
}

$resource->getMany('ResourceGroupResources')