code: public <T extends Object> T execute(Retriable retriable) throws Exception {
          return execute(retriable, DEFAULT_EXCEPTION_HANDLER);
      }
docs: Executes the action of a Retriable, and retries on error. Provides a
  way to execute a variety of methods and allow a retry to occur on
  method failure.
  
  Returns the necessary object type.
  
  This method, along with the Retriable interface is an implementation
  of the command pattern.
  
  @param retriable
  @throws Exception