merci-8.x-2.x-dev/modules/merci_test_content/merci_test_content.install

<?php

function merci_test_content_uninstall() {

  $nodes = \Drupal::entityTypeManager()->getStorage('node')->loadByProperties(['type' => 'merci_resource']);
  foreach ($nodes as $node) {
    $node->delete();
  }
  $nodes = \Drupal::entityTypeManager()->getStorage('node')->loadByProperties(['type' => 'office_hours']);
  foreach ($nodes as $node) {
    $node->delete();
  }
  $nodes = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties(['vid' => 'resource_tree']);
  foreach ($nodes as $node) {
    $node->delete();
  }
}