code: @Override
      public void setCharset(Charset cs, boolean fixedCharset)
      {
          if (includeLevel.in instanceof ModifiableCharset)
          {
              ModifiableCharset sr = (ModifiableCharset) includeLevel.in;
              sr.setCharset(cs, fixedCharset);
          }
          else
          {
              throw new UnsupportedOperationException("setting charset not supported with current input "+includeLevel.in);
          }
      }
docs: Set current character set. Only supported with byte input!
  @param cs
  @param fixedCharset
  @see org.vesalainen.parser.ParserFeature#UseModifiableCharset