Error: Call to undefined method Drupal\commerce_generate\Plugin\DevelGenerate\GenerateProducts::isDrush8()

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Error: Call to undefined method Drupal\commerce_generate\Plugin\DevelGenerate\GenerateProducts::isDrush8() in Drupal\commerce_generate\Plugin\DevelGenerate\GenerateProducts->generateProducts() (line 403 of modules/drugan/commerce_bulk/modules/commerce_generate/src/Plugin/DevelGenerate/GenerateProducts.php).