code: def test_empty_chat_message_list(self):
      prompt_builder = DynamicChatPromptBuilder(
          runtime_variables=["documents"]
      )
  
      with pytest.raises(ValueError):
          prompt_builder._process_chat_messages(
              prompt_source=[], template_variables={}
          )
  
file_path: haystack/test/components/builders/test_dynamic_chat_prompt_builder.py
imports: from typing import List
  import pytest
  from haystack import Pipeline
  from haystack.components.builders import DynamicChatPromptBuilder
  from haystack.dataclasses import ChatMessage
label_desc: Use image node_id 4 for calling the TestDynamicChatPromptBuilder obj's underlying member method code with example usage: obj.test_empty_chat_message_list() without return types