code: public function getPublisherForMessage(Message $message)
      {
          $attributes = $message->getAttributes();
          if (!isset($attributes['headers']) || !isset($attributes['headers'][$this->headerName])) {
              throw MissingPublisherException::noHeaderInMessage($message, $this->headerName);
          }
  
          $value = $attributes['headers'][$this->headerName];
          foreach ($this->valueMap as $hash => $values) {
              if (!in_array($value, $values, true)) {
                  continue;
              }
  
              return $this->publishers[$hash];
          }
  
          throw MissingPublisherException::noKnownPublisherFor($message);
      }
docs: Retrieves the publisher for a specified message
  
  @param Message $message
  
  @return Publisher
  
  @throws MissingPublisherException