/*!
Structures for a registry of classification codes.
The `Code` structure supports modeling of simple hierarchies of classification
codes, or classification schemes. For example, US and UK SIC codes, the North
American NAICS scheme, etc.
A classification scheme is an implementation of the
[`Registry`](../registry/trait.Registry.html) trait for `Code<T>` supporting the
lookup of code identifiers.
*/
// ------------------------------------------------------------------------------------------------
// Public Types
// ------------------------------------------------------------------------------------------------
/// Data about a single code, note that we parameterize the type
/// of the code identifier.