Do a copy of the attribute.

def copyProp(self, target):
        """Do a copy of the attribute. """
        if target is None: target__o = None
        else: target__o = target._o
        ret = libxml2mod.xmlCopyProp(target__o, self._o)
        if ret is None:raise treeError('xmlCopyProp() failed')
        __tmp = xmlAttr(_obj=ret)
        return __tmp