'Return the set of all supported features.'

def get_features(self, dedupe=True):

    if dedupe:
        features = set()
    else:
        features = []
    for feature_xml in self.findall(('{%s}feature' % self.namespace)):
        if dedupe:
            features.add(feature_xml.attrib['var'])
        else:
            features.append(feature_xml.attrib['var'])
    return features
