fn response_trailers(&self) -> Result<Vec<(String, String)>>
fn set_response_trailers(&self, headers: Vec<(&str, &str)>) -> Result<()>
fn response_trailer(&self, name: &str) -> Result<Option<String>>
fn set_response_trailer(&self, name: &str, value: Option<&str>) -> Result<()>
fn add_response_trailer(&self, name: &str, value: &str) -> Result<()>