Existing Wording: There are five mechanisms in FHIR for communicating collections of resources:

Proposed Wording: There are four mechanisms in FHIR for communicating collections of resources:

Comment:

Group, List, Bundle, and Composition are the only four mechanisms mentioned in 5.17.2. Either change the wording to "four" or add a bullet to explain the 5th mechanism (which might possibly be "contained resources" though I'm not sure if that's a "collection of resources").