Validate a branch of a tree, starting with the given @elem.

def schemaValidateOneElement(self, elem):
        """Validate a branch of a tree, starting with the given @elem. """
        if elem is None: elem__o = None
        else: elem__o = elem._o
        ret = libxml2mod.xmlSchemaValidateOneElement(self._o, elem__o)
        return ret