code: public function parseContentTypeHeader(HttpHeaders $headers): ?ContentTypeHeaderValue
      {
          if (!$headers->containsKey('Content-Type')) {
              return null;
          }
  
          $contentTypeHeaderParameters = $this->parseParameters($headers, 'Content-Type');
          $contentType = $contentTypeHeaderParameters->getKeys()[0];
  
          return new ContentTypeHeaderValue($contentType, $contentTypeHeaderParameters);
      }
docs: Parses the Content-Type header
  
  @param HttpHeaders $headers The request headers to parse
  @return ContentTypeHeaderValue|null The parsed header if one exists, otherwise null
  @throws InvalidArgumentException Thrown if the headers were incorrectly formatted