fn serialize_none(self) -> Result<()> {
        // self.serialize_unit()
        Err(Error::Message(String::from(
            "none is not implemented/serializable",
        )))
    }
// An absent optional is represented as the JSON `null`.
An absent optional is represented as the JSON `null`.
An absent optional is represented as the JSON ` null ` .
fn serialize_none(self) -> Result<()> {
        // self.serialize_unit()
        Err(Error::Message(String::from(
            "none is not implemented/serializable",
        )))
    }
fn serialize_none ( self ) -> Result < ( ) > { // self.serialize_unit() Err ( Error :: Message ( String :: from ( " " , ) ) ) }
An absent optional is represented as the JSON `null`.
An absent optional is represented as the JSON ` null ` .
self
self