def _parse_control_fields(self, fields, tag_id="<STR_LIT>"):
for field in fields:<EOL><INDENT>params = field.params<EOL>if tag_id not in params:<EOL><INDENT>continue<EOL><DEDENT>self.controlfields[params[tag_id]] = field.getContent().strip()<EOL><DEDENT>
Parse control fields.

Args:
    fields (list): list of HTMLElements
    tag_id (str):  parameter name, which holds the information, about
                   field name this is normally "tag", but in case of
                   oai_marc "id".