code: @Override
  	public String getFirst(String headerName) {
  		List<String> headerValues = headers.get(headerName);
  		return headerValues != null ? headerValues.get(0) : null;
  	}
docs: Return the first header value for the given header name, if any.
  @param headerName the header name
  @return the first header value, or {@code null} if none