Need the GET method for the flow analyzer

I'm trying to add an element to the SyndicationParser.php in Drupal 8.6.3 / feeds-8.x-3.0-alpha3

I've added the property in the SyndicationItem.php file (protected $ eventtype;), and that the mapping are correct because I can set the field to a firm value and it appears in Drupal where it is supposed to do it, with this:

$ item-> set (& # 39; eventtype & # 39 ;, & quot; Hello World & # 39;);

The other elements seem to have methods, but I do not see where they are built:

foreach ($ channel like $ delta => $ entry) {
$ item = new SyndicationItem ();
// Move the values ​​in an array as expected by the processors.
$ item-> set (& # 39; title & # 39 ;, entry-> getTitle ()) ......

If I try to mime that ($ entry-> getEventType ()) I receive this when I start the feed:

"Method: getEventType does not exist and can not be located on a
registered extension "

I went through the basic classes, FeedBase.php, FeedParser.php, but see no clue.