Function serialize
pub fn serialize<S, T>(
    value: &Option<T>,
    serializer: S,
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>where
    S: Serializer,
    T: ToString,pub fn serialize<S, T>(
    value: &Option<T>,
    serializer: S,
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>where
    S: Serializer,
    T: ToString,