Function concordium_std::deserial_hashset_no_length

pub fn deserial_hashset_no_length<R, K>(
    source: &mut R, 
    len: usize
) -> Result<HashSet<K, BuildHasherDefault<FnvHasher>, Global>, ParseError> where
    R: Read,
    K: Deserial + Eq + Hash, 

Read a HashSet as a list of keys, given some length. NB: This ensures there are no duplicates.