def id_and_revision_extractor(self, xml_elt):
return {'<STR_LIT:id>': None,<EOL>'<STR_LIT>': None,<EOL>}<EOL>
Function for generating a unique identifier for extracted embedded content;
to be used for DINGO's xml-import hook 'embedded_id_gen'.

For generic import, this function should be called exactly once, namely
on the root element, but we ignore the result and rather derive
a identifier from the hash value of the imported file.