code: public static IStandardVariableExpressionEvaluator getVariableExpressionEvaluator(final IEngineConfiguration configuration) {
          final Object expressionEvaluator =
                  configuration.getExecutionAttributes().get(STANDARD_VARIABLE_EXPRESSION_EVALUATOR_ATTRIBUTE_NAME);
          if (expressionEvaluator == null || (!(expressionEvaluator instanceof IStandardVariableExpressionEvaluator))) {
              throw new TemplateProcessingException(
                      "No Standard Variable Expression Evaluator has been registered as an execution argument. " +
                      "This is a requirement for using Standard Expressions, and might happen " +
                      "if neither the Standard or the SpringStandard dialects have " +
                      "been added to the Template Engine and none of the specified dialects registers an " +
                      "attribute of type " + IStandardVariableExpressionEvaluator.class.getName() + " with name " +
                      "\"" + STANDARD_VARIABLE_EXPRESSION_EVALUATOR_ATTRIBUTE_NAME + "\"");
          }
          return (IStandardVariableExpressionEvaluator) expressionEvaluator;
      }
docs: <p>
  Obtain the variable expression evaluator (implementation of {@link IStandardVariableExpressionEvaluator})
  registered by the Standard Dialect that is being currently used.
  </p>
  <p>
  Normally, there should be no need to obtain this object from the developers' code (only internally from
  {@link IStandardExpression} implementations).
  </p>
  
  @param configuration the configuration object for the current template execution environment.
  @return the variable expression evaluator object.