def delete(record)
      case record
      when Field
        delete_child(:fields, record)
      when SimulationField
        delete_child(:simulation_fields, record)
      when SiteSetup
        delete_site_setup
      else
        logger.warn("Unknown class (record) given to Prescription#delete: #{record.class}")
      end
    end
def delete(record)
      case record
      when Field
        delete_child(:fields, record)
      when SimulationField
        delete_child(:simulation_fields, record)
      when SiteSetup
        delete_site_setup
      else
        logger.warn("Unknown class (record) given to Prescription#delete: #{record.class}")
      end
    end
Removes the reference of the given instance from this instance.

 @param [Field, SimulationField, SiteSetup] record a child record to be removed from this instance