The issue is easy to solve if you have your text in english. But if you are using non-english text, you may not be able to embed the corresponding font. The work around is to avoid the masking (if possible).
In the second line, you dig inside the TextFormat class's sleeve and set the bold property to true. The bold property is a method contained within the format TextFormat object. There are many more properties besides bold, and you will learn all of them in time.