code: public function parseParameters(
          IHttpRequestMessage $request,
          string $headerName,
          int $index = 0
      ): IImmutableDictionary {
          return $this->headerParser->parseParameters($request->getHeaders(), $headerName, $index);
      }
docs: Parses the parameters (semi-colon delimited values for a header) for the first value of a header
  
  @param IHttpRequestMessage $request The request to parse
  @param string $headerName The name of the header whose parameters we're parsing
  @param int $index The
  @return IImmutableDictionary The dictionary of parameters for the first value