when set $has_many variable and execute get_all method i got an error in line 493
public $has_many = array("family_member" => array("model" => "Form_family_model"));
So please edit documentation to this
public $has_many = array( 'comments' => array( 'model' => 'model_comments', 'primary_key' => 'post_id' ) );
Or add this code after line 484
$options["primary_key"] = $this->primary_key;