title: RuntimeError: Unable to create link (name already exists) when I append hdf5 file?
body: <p>I am trying to append the hdf5 dataset to the previous hdf5 dataset<br/>
  following error occured</p>
  
  <blockquote>
    <p>h5o.link(obj.id, self.id, name, lcpl=lcpl, lapl=self._lapl)   File
    "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper<br>
    File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper 
    File "h5py/h5o.pyx", line 202, in h5py.h5o.link RuntimeError: Unable
    to create link (name already exists)</p>
  </blockquote>
  
  <pre><code> sal_maps = np.array([], dtype=np.float32).reshape((0,) + img_size)
          probs = np.array([], dtype=np.float32)
          preds = np.array([], dtype=np.uint8)
          for idx, (img, target) in enumerate(dataloader):
  
      # TODO problem1 idx problem
              sal_maps_b, probs_b, preds_b = self.generate_image(img, idx)
              sal_maps_b = np.transpose(sal_maps_b, axes=(3,0, 1, 2))
  
              sal_maps = np.vstack([sal_maps,sal_maps_b])
              probs = np.append(probs, probs_b)
              preds = np.append(preds,preds_b)
              #if idx ==2: break
              if idx % 100 == 0:
                  print("idx-&gt;{} sal_maps-&gt;{}, probs-&gt;{} , preds-&gt;{}".format(idx,sal_maps.shape,probs.shape,preds.shape))
  
          # TODO indent change
  
                  print("result-&gt;{}".format(sal_maps.size))
                  with h5py.File(self.datapath, 'a') as hf:
                      hf.create_dataset('saliencys', data=sal_maps)
                      hf.create_dataset('probs', data=probs)
                      hf.create_dataset('preds', data=preds)
                      hf.close()
                  sal_maps = np.array([], dtype=np.float32).reshape((0,) + img_size)
                  probs = np.array([], dtype=np.float32)
                  preds = np.array([], dtype=np.uint8)
                  print('Save_saliency_maps::',idx)
  </code></pre>