YourModel.php

<?php
namespace Some\Model;

class YourModel {
  
  /**
   * @var Collection<Asdf>
   */
  protected $asdfs;
  
  ...
  
  /**
   * @return Asdf[]
   */
  public function getAsdfs() {
    // loads the collection, so not always a good idea
    return $this->asdfs->toArray();
  }
  
}