code: private function getCustomersMap()
      {
          /** @var \Praxigento\Downline\Repo\Data\Customer[] $customers */
          $customers = $this->daoCustDwnl->get();
          $result = $this->hlpTree->mapById($customers, ECustomer::A_CUSTOMER_REF);
          return $result;
      }
docs: Actual customers downline mapped by customer ID.
  
  @return \Praxigento\Downline\Repo\Data\Customer[]