pub trait ValueExt {
// Required methods
fn str_or<'a>(&'a self, key: &str, default: &'a str) -> &'a str;
fn u64_or(&self, key: &str, default: u64) -> u64;
fn bool_or(&self, key: &str, default: bool) -> bool;
fn str_array_join(&self, key: &str, sep: &str) -> String;
}