def map_namespace(self, plain_src_ns):
        """Given a plain source namespace, return the corresponding plain
        target namespace, or None if it is not included.
        """
        namespace = self.lookup(plain_src_ns)
        if namespace:
            return namespace.dest_name
        return None
def map_namespace ( self , plain_src_ns ) : namespace = self . lookup ( plain_src_ns ) if namespace : return namespace . dest_name return None
Given a plain source namespace, return the corresponding plain
        target namespace, or None if it is not included.