pub meta: MetadataMap,

        let (flag, amount, cost, price) = Default::default();

        let (flag, amount, cost, price, meta) = Default::default();

            meta,

    pub fn add_meta(
        &mut self,
        key: impl Into<MetadataKey>,
        value: impl Into<MetadataValue>,
    ) -> &mut Self {
        self.meta.insert(key.into(), value.into());
        self
    }
    #[inline]

        self
    }
    #[inline]
    pub fn clear_meta(&mut self) -> &mut Self {
        self.meta.clear();

        self
    }
    #[inline]
    pub fn set_meta(&mut self, meta: impl Into<MetadataMap>) -> &mut Self {
        self.meta = meta.into();

            meta,

        }
        for (key, value) in meta {
            write!(f, "\n    {key}: {value}")?;

            meta,

        }
        for (key, value) in meta {
            write!(self.inner, "\n    {key}: {value}")?;