RFC-836 requires some new entries be added to ObservationInfo:

• has_simulated_content: Boolean to indicate that some part of this observation was taken in a simulated state.
• group_counter_start and group_counter_end indicating the first and last observation "counter" values for the visit of which this observation is a member.

The defaults for the base class can be False for is_simulated and observation_counter for the visit counters.