expand a qualified name's namespace prefix to include the resolved
        namespace root url

def _expand_qname(self, qname):
        """expand a qualified name's namespace prefix to include the resolved
        namespace root url"""
        if type(qname) is not rt.URIRef:
            raise TypeError("Cannot expand qname of type {}, must be URIRef"
                            .format(type(qname)))
        for ns in self.graph.namespaces():
            if ns[0] == qname.split(':')[0]:
                return rt.URIRef("%s%s" % (ns[1], qname.split(':')[-1]))
        return qname