code: def test_get_placeholders_empty(self):
      placeholders = prompt_utils.get_placeholders("")
      self.assertEmpty(placeholders)
  
      placeholders = prompt_utils.get_placeholders(
          "There are no placeholders here"
      )
      self.assertEmpty(placeholders)
  
imports: from __future__ import annotations
  from absl.testing import absltest
  from google.generativeai.notebook.lib import prompt_utils
label_desc: Use image node_id 1 for calling the PromptUtilsTest obj's underlying member method code with example usage: obj.test_get_placeholders_empty() without return types