code: @Override
      public ListStateMachinesResult listStateMachines(ListStateMachinesRequest request) {
          request = beforeClientExecution(request);
          return executeListStateMachines(request);
      }
docs: <p>
  Lists the existing state machines.
  </p>
  <p>
  If <code>nextToken</code> is returned, there are more results available. The value of <code>nextToken</code> is a
  unique pagination token for each page. Make the call again using the returned token to retrieve the next page.
  Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination
  token will return an <i>HTTP 400 InvalidToken</i> error.
  </p>
  <note>
  <p>
  This operation is eventually consistent. The results are best effort and may not reflect very recent updates and
  changes.
  </p>
  </note>
  
  @param listStateMachinesRequest
  @return Result of the ListStateMachines operation returned by the service.
  @throws InvalidTokenException
  The provided token is invalid.
  @sample AWSStepFunctions.ListStateMachines
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/states-2016-11-23/ListStateMachines" target="_top">AWS API
  Documentation</a>