code: protected function processAttachments(array $attachments)
      {
          $attachments = AttachmentUtils::processAttachments($attachments);
  
          $processedAttachments = [];
          foreach ($attachments as $name => $attachment) {
              $item = [
                  'Name'        => $name,
                  'Content'     => base64_encode($this->getAttachmentContent($attachment)),
                  'ContentType' => $attachment->getType(),
              ];
  
              $id = $attachment->getId();
              if (isset($id)) {
                  $item['ContentID'] = $id;
              }
  
              $processedAttachments[] = $item;
          }
  
          return $processedAttachments;
      }
docs: @param Attachment[] $attachments
  
  @return array An array containing arrays of the following format:
  array(
  'Name'                 => name,
  'Content'              => base64-encoded content,
  'ContentType'          => type,
  (optional) 'ContentID' => id,
  )