Search a Ns aliasing a given URI. Recurse on the parents
          until it finds the defined namespace or return None
           otherwise.

def searchNsByHref(self, node, href):
        """Search a Ns aliasing a given URI. Recurse on the parents
          until it finds the defined namespace or return None
           otherwise. """
        if node is None: node__o = None
        else: node__o = node._o
        ret = libxml2mod.xmlSearchNsByHref(self._o, node__o, href)
        if ret is None:raise treeError('xmlSearchNsByHref() failed')
        __tmp = xmlNs(_obj=ret)
        return __tmp