<?php
        $aop_args = array(
          'post_type' => 'areas_of_practice',
          'post_status' => 'publish',
          'post_parent' => 0,
          'order_by' => 'menu_order',
          'order' => 'ASC',
        );
        $the_query = new WP_Query( $aop_args );
        if ( $the_query->have_posts() ) :
          while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
          <li class="parent_aop">
            <a class="parent-wrapper" href="<?php the_permalink(); ?>">
            <?php
            if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
                 the_post_thumbnail('medium');
             } ?>
             <span><?php the_title(); ?></span>
           </a>
            <ul class="child_list">
            <?php
            $theparentid = get_the_id();
            //echo $theparentid;

            $aop_child_args = array(
              'post_type' => 'areas_of_practice',
              'post_status' => 'publish',
              'post_parent' => $theparentid,
              'order_by' => 'menu_order',
              'order' => 'ASC',
            );

            $the_child_query = new WP_Query( $aop_child_args );
            if ( $the_child_query->have_posts() ) :
              while ( $the_child_query->have_posts() ) : $the_child_query->the_post(); ?>
                <li class="child_aop">
                <a href="<?php the_permalink(); ?>"> <?php the_title(); ?> </a>
                </li>
                <?php
                $thechildid = get_the_id();
                //echo $thechildid;
            endwhile;
          endif;
          ?>
          </ul>
          </li>
          <?php
          endwhile;
        endif;
        wp_reset_query();
      ?>