Find all sites of a default class

[edwardjjj]

Hi, I'm trying to filter sites based on class names. According to documentation, The following code will return the class name mjcf_model.find_all('site')[0].dclass But instead, it returned an MJCF Element, mjcf_model.find_all('site')[0].dclass.dclass will return the actual class name. This makes filtering sites based on class names very ugly because sites with no default class names will return None, then doing mjcf_model.find('site','mysite').dclass.dclass will result in errors.