pub fn unknown(message: impl Into<String>) -> Status {
        Status::new(Code::Unknown, message)
    }
Unknown error. An example of where this error may be returned is if a
`Status` value received from another address space belongs to an error-space
that is not known in this address space. Also errors raised by APIs that
do not return enough error information may be converted to this error.
tonic/src/status.rs