Clarification on difference between FontStyle.NONE and FontStyle.NotSet

[devunt]

I'm currently building a code block extension for Tiptap using Shiki as a syntax highlighter.
To map shiki's tokens to prosemirror decorations, I'm using codeToTokens method that returns stream of ThemedTokens.

One of the property of ThemedToken is a fontStyle, which indeed has type signature of FontStyle enum.
FontStyle enum has following 5 members: NotSet, None, Italic, Bold, Underline. Last three values' meaning are clear, but I'm not sure what does NotSet and None means.

Currently I'm assuming that NotSet means the font style is not defined, so the renderer should not set any font style properties and let the node naturally inherits the styles from its parent. And None means that the font style is literally "none", so the renderer should reset the corresponding font style properties to their default values which forces node renders as a normal text even if the parent node's font style is Bold or Italic or something.

I'm attaching the code that I'm using now for a better understanding.

  if (token.fontStyle === FontStyle.None) {
    style['font-style'] = 'normal';
    style['font-weight'] = 'normal';
    style['text-decoration'] = 'none';
  } else if (token.fontStyle === FontStyle.Bold) {
    style['font-weight'] = 'bold';
  } else if (token.fontStyle === FontStyle.Italic) {
    style['font-style'] = 'italic';
  } else if (token.fontStyle === FontStyle.Underline) {
    style['text-decoration'] = 'underline';
  }

[devunt]

After searching a code base, I found out that shiki exports getTokenStyleObject and stringifyTokenStyle functions. Is it safe to use theses functions? I'm worried that they are some undocumented functions and should not be relied on.