code: function emphasis(node) {
    var marker = this.options.emphasis
    var content = this.all(node).join('')
  
    // When in pedantic mode, prevent using underscore as the marker when there
    // are underscores in the content.
    if (
      this.options.pedantic &&
      marker === underscore &&
      content.indexOf(marker) !== -1
    ) {
      marker = asterisk
    }
  
    return marker + content + marker
  }
docs: Stringify an `emphasis`.  The marker used is configurable through `emphasis`, which defaults to an underscore (`'_'`) but also accepts an asterisk (`'*'`):  ```markdown *foo* ```  In `pedantic` mode, text which itself contains an underscore will cause the marker to default to an asterisk instead:  ```markdown *foo_bar* ```