@hep.over('<STR_LIT>', '<STR_LIT>')<EOL>@utils.for_each_value<EOL>def isbns(self, key, value):
def _get_medium(value):<EOL><INDENT>def _normalize(medium):<EOL><INDENT>schema = load_schema('<STR_LIT>')<EOL>valid_media = schema['<STR_LIT>']['<STR_LIT>']['<STR_LIT>']['<STR_LIT>']['<STR_LIT>']['<STR_LIT>']<EOL>medium = medium.lower().replace('<STR_LIT:->', '<STR_LIT>').replace('<STR_LIT:U+0020>', '<STR_LIT>')<EOL>if medium in valid_media:<EOL><INDENT>return medium<EOL><DEDENT>elif medium == '<STR_LIT>':<EOL><INDENT>return '<STR_LIT>'<EOL><DEDENT>elif medium == '<STR_LIT>':<EOL><INDENT>return '<STR_LIT>'<EOL><DEDENT>return '<STR_LIT>'<EOL><DEDENT>medium = force_single_element(value.get('<STR_LIT:b>', '<STR_LIT>'))<EOL>normalized_medium = _normalize(medium)<EOL>return normalized_medium<EOL><DEDENT>def _get_isbn(value):<EOL><INDENT>a_value = force_single_element(value.get('<STR_LIT:a>', '<STR_LIT>'))<EOL>normalized_a_value = a_value.replace('<STR_LIT:.>', '<STR_LIT>')<EOL>if normalized_a_value:<EOL><INDENT>return normalize_isbn(normalized_a_value)<EOL><DEDENT><DEDENT>return {<EOL>'<STR_LIT>': _get_medium(value),<EOL>'<STR_LIT:value>': _get_isbn(value),<EOL>}<EOL>
Populate the ``isbns`` key.