parse an XML in-memory document and build a tree. This
           reuses the existing @ctxt parser context

def htmlCtxtReadDoc(self, cur, URL, encoding, options):
        """parse an XML in-memory document and build a tree. This
           reuses the existing @ctxt parser context """
        ret = libxml2mod.htmlCtxtReadDoc(self._o, cur, URL, encoding, options)
        if ret is None:raise treeError('htmlCtxtReadDoc() failed')
        __tmp = xmlDoc(_obj=ret)
        return __tmp