code: def test_nlg_schema_validation_empty_buttons():
      content = {"text": "Hey there!", "buttons": []}
      assert CallbackNaturalLanguageGenerator.validate_response(content)
  
imports: import uuid
  from typing import Text, Any
  import jsonschema
  import pytest
  from sanic import Sanic, response
  from rasa.core.nlg.callback import CallbackNaturalLanguageGenerator
  from rasa.core.nlg.response import TemplatedNaturalLanguageGenerator
  from rasa.utils.endpoints import EndpointConfig, read_endpoint_config
  from rasa.core.agent import Agent
label_desc: Use image node_id 5 for calling a global function with example usage: test_nlg_schema_validation_empty_buttons() without return types