title: How to list all datasets in h5py file?
body: <p>I have a h5py file storing numpy arrays, but I got <code>Object doesn't exist error</code> when trying to open it with the dataset name I remember, so is there a way I can list what datasets the file has? </p>
  
  <pre><code>   with h5py.File('result.h5','r') as hf:
          #How can I list all dataset I have saved in hf?
  </code></pre>