code: public void bodyWillLeave (BodyObject body)
      {
          _plobj.startTransaction();
          try {
              // remove their occupant info (which is keyed on oid)
              _plobj.removeFromOccupantInfo(body.getOid());
              // and remove them from the occupant list
              _plobj.removeFromOccupants(body.getOid());
          } finally {
              _plobj.commitTransaction();
          }
      }
docs: Called to inform a manager that a body is about to leave this place. This will be followed
  by a call to {@link #bodyLeft} once all events relating to body entry have been processed.