This atom marks a Java class (or interface) for serialization in HyperGraph
storage. More concretely, all its sub-types (interfaces or classes) will
be mapped to HyperGraph types to work directly with the private fields
similarly to what standard Java serialization thus, as opposed to accessible
object property through the Java beans getter/setter idiom. However, unlike
standard Java serialization which is binary, the HyperGraph representation still
relies on records and slots, thus making the data indexable and searcheable, albeit
with the ensuing slower instantiation time.