How to add class to bbPress bbp_get_topic_author_link()?

How can I add a class with bbp_get_topic_author_link() function.

I want to add a class in the image, am trying to do like below:

   <?php 
      printf( 
      bbp_get_topic_author_link( 

        array( 
          'type' => 'avatar', 
          'size' => '75',
          'class' => 'my-class-goes-here'
       ) 

     )

    ) ; ?>

But still not working.