code: public void setFontFamily(String header_font_family, String details_font_family) {
          this.headerLabel
                  .setStyle("-fx-font-family: \"" + header_font_family + "\";");
          this.detailsLabel
                  .setStyle("-fx-font-family: \"" + details_font_family + "\";");
      }
docs: Sets both font families for the header and the details label with two
  font families <code>String</code> parameters given.
  
  @param header_font_family The header font family in <code>Strings</code>
  @param details_font_family The details font family in
  <code>Strings</code>