Hi im trying to get the sitetree to show inside the dataobjectmanager popup, heres what im hoping to achieve

1) upload a set of images
2) apply captions and titles to each
3) add an internal link that echos out on page inside a span. (like a "read more")

1) and 2) are no problem, working great, applying the sitetree however is giving me grief, this is what i have..

My Class file:

<?php 
class HomepageImageResource extends DataObject
{
    static $db = array (
        'HomepageTitle' => 'Text',
        'HomepageCaption' => 'Text'
    );
 
    static $has_one = array (
        'HomepageAttachment' => 'Image',
        'HomepageInternalLink' => "SiteTree"  
    );
 
    public function getCMSFields_forPopup()
    {
        return new FieldSet(
            new TextField('HomepageTitle'),
            new TextareaField('HomepageCaption'),
            new FileIFrameField('HomepageAttachment')
        //    new SimpleTreeDropdownField( 'HomepageInternalLinkID', 'HomepageInternalLink', 'SiteTree' )
       );
    }
}

now onto my HomePage extends Page: (note the "// this causes me the error" comment) without that line all works ok but no sitetree

class HomePage extends Page {
   static $db = array( 
   );
   static $has_one = array(
   );
   
   static $has_many = array (
        'HomepageImages' => 'HomePageImageResource'
    );
   
   function getCMSFields() {
       
      $fields = parent::getCMSFields();
      
      $fields->removeFieldFromTab('Root.Content.Main', 'Content');
      
       $fields = parent::getCMSFields();
        $homepagemanager = new ImageDataObjectManager(
            $this, // Controller
            'HomepageImages', 
            'HomepageImageResource',
            'HomepageAttachment',
            'HomepageInternalLink',                   // this causes me the error"
      
            array(
                'HomepageTitle' => 'HomepageTitle', 
                'HomepageCaption' => 'HomepageCaption'
            ), // Headings 
            'getCMSFields_forPopup'
        );
        $fields->addFieldToTab("Root.Content.Main",$homepagemanager);
        
        $fields->removeFieldFromTab('Root.Content.Main', 'MainPageContent'); 

   return $fields;
 }
   
   
}

UPDATE: Marked as Solved
this is what i needed to do to get it working if anyone else comes across this issue:

In HomePage.php i changed the getCMSFields() function to:

function getCMSFields() {
       
      $fields = parent::getCMSFields();
      
      $fields->removeFieldFromTab('Root.Content.Main', 'Content');
      
       $fields = parent::getCMSFields();
        $homepagemanager = new ImageDataObjectManager(
            $this, // Controller
            'HomepageImages', // Source name
            'HomepageImageResource', // Source class
            'HomepageAttachment', // File name on DataObject
            //'HomepageInternalLink',
      
            array(
                'HomepageTitle' => 'HomepageTitle', 
                'HomepageCaption' => 'HomepageCaption'
            ),  
            'getCMSFields_forPopup'
        );
        
        $homepagemanager->setRelationAutoSetting(false);
        
        $fields->addFieldToTab("Root.Content.Main",$homepagemanager);
        
        $fields->removeFieldFromTab('Root.Content.Main', 'MainPageContent'); 

   return $fields;
 }

overriding default setRelationAutoSetting to false