code: def test_execution_variable():
      var = ExecutionVariables.START_DATETIME
      assert var.expr == {"Get": "Execution.StartDateTime"}
  
imports: from __future__ import absolute_import
  import pytest
  from sagemaker.workflow.execution_variables import ExecutionVariables
label_desc: Use image node_id 1 for calling a global function with example usage: test_execution_variable() without return types