| BuilderUtils | 
 A wrapper around ImmutableList builder that produces immutable lists if elements are added to the
 builder or a collapsed list otherwise. 
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| Collapsed.Exceptions | 
 Attempting to access a property of a collapsed object should throw an exception, indicating that it was not in the
 original request. 
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| EnrichableMap<K,V> | 
 A map with the RestEnrichable annotation, indicating that this map should be converted to a RestEntity
 and enriched by the REST stack. 
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| ExpandedReference<T> | 
 An expanded reference has a value, call get() will return that referent value. 
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| ModelListBuilder<T> | 
 Assists in building fields that may be either a list of items or an explicit CollapsedList. 
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| ModelMapBuilder<K,V> | 
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| Reference<T> | 
 A reference to a model object. 
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