Roles and Capabilities filters

Need to display the coauthorplus metabox with author capabilities. On the plugin documentation, it says its only with super_admin and editor that the metabox is available. Any idea to add a filter in the functions.php file to make the metabox displayed for author’s role?

function coauthorplus_cap(){
  if( current_user() ) == 'author' ){
  // what should I say?
  return true;
  }
}
add_filter ('coauthors_plus_edit_authors', 'coauthorplus_cap');

Thx for your help