code: @SuppressWarnings("unchecked")
      public String getCharSet() {
          ParameterParser parser = new ParameterParser();
          parser.setLowerCaseNames(true);
          // Parameter parser can handle null input
          Map<String, String> params = parser.parse(getContentType(), ';');
          return params.get("charset");
      }
docs: Returns the content charset passed by the agent or {@code null} if not defined.
  
  @return the content charset passed by the agent or {@code null} if not defined