def update_system_numbers(self):
scn_035_fields = record_get_field_instances(self.record, '<STR_LIT>')<EOL>forbidden_values = ["<STR_LIT>",<EOL>"<STR_LIT>",<EOL>"<STR_LIT>",<EOL>"<STR_LIT>",<EOL>"<STR_LIT>",<EOL>"<STR_LIT>"]<EOL>for field in scn_035_fields:<EOL><INDENT>subs = field_get_subfields(field)<EOL>if '<STR_LIT>' in subs:<EOL><INDENT>if '<STR_LIT:a>' not in subs:<EOL><INDENT>continue<EOL><DEDENT>for sub in subs['<STR_LIT>']:<EOL><INDENT>if sub.lower() in forbidden_values:<EOL><INDENT>break<EOL><DEDENT><DEDENT>else:<EOL><INDENT>suffixes = [s.lower() for s in subs['<STR_LIT>']]<EOL>if '<STR_LIT>' in suffixes:<EOL><INDENT>new_subs = [('<STR_LIT:a>', '<STR_LIT>' % subs['<STR_LIT:a>'][<NUM_LIT:0>])]<EOL>record_add_field(<EOL>self.record, '<STR_LIT>', subfields=new_subs)<EOL>continue<EOL><DEDENT><DEDENT><DEDENT>if '<STR_LIT:a>' in subs:<EOL><INDENT>for sub in subs['<STR_LIT:a>']:<EOL><INDENT>if sub.lower() in forbidden_values:<EOL><INDENT>record_delete_field(self.record, tag="<STR_LIT>",<EOL>field_position_global=field[<NUM_LIT:4>])<EOL><DEDENT><DEDENT><DEDENT><DEDENT>
035 Externals.