def log(execution_id = nil)
      execution_id = @execution_id if execution_id.nil?
      log_json = @service.get_log(@id, execution_id)
      VcoWorkflows::WorkflowExecutionLog.new(log_json)
    end
def log(execution_id = nil)
      execution_id = @execution_id if execution_id.nil?
      log_json = @service.get_log(@id, execution_id)
      VcoWorkflows::WorkflowExecutionLog.new(log_json)
    end
Return logs for the given execution
 @param [String] execution_id optional execution id to get logs for
 @return [VcoWorkflows::WorkflowExecutionLog]