I have figured out the solution…
### solution ######            
  
# reshape the dataset          
xxx = xx.reshape(2,5,7)  

# create two tensorflow datasets
input_dataset0 = timeseries_dataset_from_array(xxx[0,:,:],
                                                      None,
                                                      sequence_length,
                                                      sequence_stride=stride,
                                                      sampling_rate=rate)
input_dataset1 = timeseries_dataset_from_array(xxx[1,:,:],
                                                      None,
                                                      sequence_length,
                                                      sequence_stride=stride,
                                                      sampling_rate=rate)
# concatenate the two tensorflow datasets
input_dataset = input_dataset0.concatenate(input_dataset1)

x_test = np.concatenate([x for x in input_dataset], axis=0)