| Class Summary | 
| BuilderUtils | A wrapper around ImmutableList builder that produces immutable lists if elements are added to the
 builder or a collapsed list otherwise. | 
| Collapsed.Exceptions | Attempting to access a property of a collapsed object should throw an exception, indicating that it was not in the
 original request. | 
| CollapsedReference<T> | A collapsed reference is a property that potentially has a value, but the property's
 value has not been expanded at the time fo the request. | 
| EmptyReference<T> | A null object reference, indicates that the referenced property is empty. | 
| ExpandedReference<T> | An expanded reference has a value, call get() will return that referent value. | 
| Reference<T> | A reference to a model object. |