CSS class predefined in a custom block / template

I'm trying and learning to build a custom block / template for Gutenberg and I'd like to "pre-define" a CSS class for a specific block. Is it possible to add it as below?

Refer: [Template and Block][1]

For example, CSS class defined for one of the headers blockHeadStyle:

myplugin_register_book_post_type () {function
$ args = array (
& # 39; public & # 39; => true,
& # 39; Label & # 39; => & # 39; Books & # 39 ;,
& # 39; show_in_rest & # 39; => true,
& # 39; template & # 39; => array (
array (& # 39; core / image & # 39 ;, array (
& # 39; align & # 39; => & # 39; left
)),
array (& # 39; kernel / header & # 39;
& # 39; placeholder & # 39; => & # 39; Add an author ... & # 39;
& # 39; class & # 39; => & # 39; blockHeadStyle & # 39;
)),
array (& kernel / paragraph & # 39 ;, array (
& # 39; placeholder & # 39; => & # 39; Add a description ... & # 39;
)),
)
)
register_post_type (& # 39; book & # 39 ;, args);
}
add_action (& # 39; init & # 39 ;, & quot; myplugin_register_book_post_type & quot;);