This module implements the URI class.
Objects of this class represent "Uniform Resource Identifier references" as
specified in RFC 2396 (and updated by RFC 2732).

A Uniform Resource Identifier is a compact string of characters that
identifies an abstract or physical resource.
A Uniform Resource Identifier can be further classified as either a
Uniform Resource Locator (URL) or a Uniform Resource Name (URN).
The distinction between URL and URN does not matter to the URI class interface.
A "URI-reference" is a URI that may have additional information attached in
the form of a fragment identifier.

An absolute URI reference consists of three parts: a scheme, a scheme-specific
part and a fragment identifier.
A subset of URI references share a common syntax for hierarchical namespaces.
For these, the scheme-specific part is further broken down into authority,
path and query components.
These URIs can also take the form of relative URI references, where the scheme
(and usually also the authority) component is missing, but implied by the
context of the URI reference.