Function get_or_default

pub fn get_or_default<T, HashFn, R>(hash: &HashFn, key: &[u8]) -> T
where
    T: Decode + Sized + Default,
    HashFn: Fn(&[u8]) -> R,
    R: AsRef<[u8]>,

Return the value of the item in storage under key, or the type’s default if there is no explicit entry.