code: private function buildContributorsList(array $issues) : array
      {
          $contributors = [];
  
          foreach ($issues as $issue) {
              foreach ($issue->getContributors() as $contributor) {
                  $contributors[$contributor] = $contributor;
              }
          }
  
          return array_values($contributors);
      }
docs: @param Issue[] $issues
  
  @return string[]