Split `qname` into namespace URI and local name

        Return namespace and local name as a tuple. This is a static
        method.

def split_qname(qname):
        """Split `qname` into namespace URI and local name

        Return namespace and local name as a tuple. This is a static
        method."""
        res = qname.split(YinParser.ns_sep)
        if len(res) == 1:       # no namespace
            return None, res[0]
        else:
            return res