The bodySite extension is currently included as Observation.extension(bodySite) - this inclusion is against the defined purpose of the extension and it's context of use, i.e. Element.
The extension needs to be on Observation.bodySite so that it becomes Observation.bodySite.extension(bodySite).
The bodySite extension is currently included as Observation.extension(bodySite) - this inclusion is against the defined purpose of the extension and it's context of use, i.e. Element.
The extension needs to be on Observation.bodySite so that it becomes Observation.bodySite.extension(bodySite).