_inherit_context(self, node) -> list
        Scan ancestors of attribute and namespace context.  Used only
        for single element node canonicalization, not for subset
        canonicalization.

def _inherit_context(self, node):
        '''_inherit_context(self, node) -> list
        Scan ancestors of attribute and namespace context.  Used only
        for single element node canonicalization, not for subset
        canonicalization.'''

        # Collect the initial list of xml:foo attributes.
        xmlattrs = filter(_IN_XML_NS, _attrs(node))

        # Walk up and get all xml:XXX attributes we inherit.
        inherited, parent = [], node.parentNode
        while parent and parent.nodeType == Node.ELEMENT_NODE:
            for a in filter(_IN_XML_NS, _attrs(parent)):
                n = a.localName
                if n not in xmlattrs:
                    xmlattrs.append(n)
                    inherited.append(a)
            parent = parent.parentNode
        return inherited