Indicates that method is used to retrieve current workflow state. The method
 is expected to perform read only access of the workflow implementation object
 and is invoked synchronously which disallows use of any asynchronous
 operations (like calling methods annotated with 
Asynchronous).
 
 Method is expected to have empty list of parameters.
 
Promise or 
void return types are not allowed for the annotated method.
 
 The generated external client implementation uses {@link AmazonSimpleWorkflow#describeWorkflowExecution(com.amazonaws.services.simpleworkflow.model.DescribeWorkflowExecutionRequest) 
 visibility API to retrieve the state. It allows access to the sate using external client if decider 
 workers are down and even after workflow execution completion.