Make it transient

<?php
 add_action( 'save_post', 'ssc_reset_areas_transient' );
 function ssc_get_areas_list(){
  if ( false === ( $areas_data = get_transient( 'areas_of_practice') ) ) {
    ssc_set_areas_transient( );
    $areas_data = get_transient( 'areas_of_practice' );
  }
  return $attorney_data;
}
 function ssc_set_areas_transient() {
  $nested_posts = array();
  $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();
      $theparentid = get_the_id();

      $aop_child_args = array(
        'post_type' => 'areas_of_practice',
        'post_status' => 'publish',
        'post_parent' => $theparentid,
        'order_by' => 'menu_order',
        'order' => 'ASC',
      );
      $child_posts = array();
      $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();
          $thechildid = get_the_id();
          $child_posts[] = $thechildid;
      endwhile;
    endif;
    $nested_posts[$theparentid][] = $child_posts;
    endwhile;
    set_transient( 'areas_of_practice', $nested_posts, 52 & WEEK_IN_SECONDS );
  endif;
  wp_reset_query();
}
function ssc_reset_areas_transient( $post_id ) {
  delete_transient( 'areas_of_practice' );
  ssc_set_areas_transient();
}
?>