@hep2marc.over('<STR_LIT>', '<STR_LIT>')<EOL>@utils.for_each_value<EOL>def isbns2marc(self, key, value):
return {<EOL>'<STR_LIT:a>': value.get('<STR_LIT:value>'),<EOL>'<STR_LIT:b>': value.get('<STR_LIT>'),<EOL>}<EOL>
Populate the ``020`` MARC field.