code: def test_to_string_on_join():
      func = Join(values=[1, "a", False, 1.1])
  
      assert func.to_string() == func
  
file_path: sagemaker-python-sdk/tests/unit/sagemaker/workflow/test_functions.py
imports: from __future__ import absolute_import
  import pytest
  from sagemaker.workflow.execution_variables import ExecutionVariables
  from sagemaker.workflow.functions import Join, JsonGet
  from sagemaker.workflow.parameters import ParameterFloat, ParameterInteger, ParameterString
  from sagemaker.workflow.properties import Properties, PropertyFile
label_desc: Use image node_id 4 for calling a global function with example usage: test_to_string_on_join() without return types