code: public function registerReporter(ReporterInterface $reporter)
      {
          $format = $reporter->getFormat();
  
          if (isset($this->reporters[$format])) {
              throw new \UnexpectedValueException(sprintf('Reporter for format "%s" is already registered.', $format));
          }
  
          $this->reporters[$format] = $reporter;
  
          return $this;
      }
docs: @param ReporterInterface $reporter
  
  @return $this