code: def create_default_collection_event_parameters(rep)
        cep = parent.collection_event_parameters if parent
        user = cep.user if cep
        user ||= scg_collector || rep.user || return
        cep = CaTissue::CollectionEventParameters.new(:specimen => self, :user => user)
        logger.debug { "Created default #{qp} collection event #{cep.qp}." }
        cep
      end
docs: The default CEP user is, by order of preference:
   * this specimen's parent specimen collector
   * this specimen's SCG collector
   * the receiver
  
   @param [CaTissue::ReceivedEventParameters] the required REP
   @return [CaTissue::CollectionEventParameters] the default CEP