public @interface ShallowCopyState
State implementations that indicates that their copy operation is shallow.
When modifying copied states that use a shallow copy, the variable values should always be copied before modifying
them, so that the values in the state from which they were copied are not modified. That is, use copy-on-write.
Typically, the MutableState.set(Object, Object) for shallow copied states will
always implement a copy-on-write that is safe.