only in patch2:
unchanged:
--- a/core/modules/user/src/Plugin/migrate/source/UserPictureInstance.php
+++ b/core/modules/user/src/Plugin/migrate/source/UserPictureInstance.php
@@ -39,15 +39,6 @@ public function initializeIterator() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
-    // This source provides a single row, corresponding to a single picture
-    // field to be added to the user entity.
-    return 1;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function fields() {
     return array(
       'file_directory' => 'The directory to store images..',
@@ -59,6 +50,13 @@ public function fields() {
   /**
    * {@inheritdoc}
    */
+  public function query() {
+    // Nothing to do here.
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getIds() {
     $ids['id']['type'] = 'string';
     return $ids;