Macro write_variadic 

macro_rules! write_variadic {
    (ArgumentBufferError = $argbuf_error_type:ty; $sql:expr, $value1:expr) => { ... };
    (ArgumentBufferError = $argbuf_error_type:ty; $sql:expr, $value1:expr, $($valuex:expr),*) => { ... };
    ($sql:expr, $value1:expr, $($valuex:expr),*) => { ... };
}