'Return an ElementTree containing the xml for the specified
verbnet class.
:param fileid_or_classid: An identifier specifying which class
should be returned.  Can be a file identifier (such as
``\'put-9.1.xml\'``), or a verbnet class identifier (such as
``\'put-9.1\'``) or a short verbnet class identifier (such as
``\'9.1\'``).'

def vnclass(self, fileid_or_classid):

    if (fileid_or_classid in self._fileids):
        return self.xml(fileid_or_classid)
    classid = self.longid(fileid_or_classid)
    if (classid in self._class_to_fileid):
        fileid = self._class_to_fileid[self.longid(classid)]
        tree = self.xml(fileid)
        if (classid == tree.get(u'ID')):
            return tree
        else:
            for subclass in tree.findall(u'.//VNSUBCLASS'):
                if (classid == subclass.get(u'ID')):
                    return subclass
            else:
                assert False
    else:
        raise ValueError((u'Unknown    identifier    %s' % fileid_or_classid))
