docs: 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