Function protobuf::rt::compute_map_size

pub fn compute_map_size<K, V>(
    field_number: u32, 
    map: &HashMap<K::Value, V::Value>
) -> u32 where
    K: ProtobufType,
    V: ProtobufType,
    K::Value: Eq + Hash, 

Compute serialized size of map field and cache nested field sizes.