drop_first: usize

    pub drop_first: usize

    pub (crate) fn drop_first(&self) -> usize {
        self.0.drop_first
    }

        // println!("{}", DataSelector::from_file("germany_selector.keytree")
        //     .into_data_spec()
        //     .unwrap()
        //     .keytree());

                    drop_first:     series_spec.drop_first,

        dbg!(path);

    pub drop_first:     Option<usize>,

        if let Some(drop) = &self.drop_first {
            kt.push_value(1, "drop_first", drop);
        }

        if let ParserSpec::FredDailySpec(_) = self.parser {
            kt.push_value(1, "parse_cat", "fred_daily")
        };
        if let ParserSpec::FredSpec(parser_spec) = self.parser {
            if parser_spec.drop_first != 0 {
                kt.push_key(1, "parser");
                kt.push_value(2, "drop_first", parser_spec.drop_first.to_string());
            }
        };

//     series:
//         data_type:          int
//         country:            United States
//         series_id:          DPRIME
//         parse_cat:          fred_daily
// 
// seriess:
//     series:
//         country:    United States
//         data_type:  int
//         series_id:  DPRIME

            (true, true)    => Err(keytree_selection_failed(file!(), line!()))?,

            (true, true)    => Err(custom(file!(), line!(), "Only one parser allowed."))?,

                drop_first: self.opt_value("series::drop_first")?,

                        drop_first: None, 

                        drop_first: None,