title: 'No schema registered' in ONNX model conversion
body: <p>I am using kaggle notebook. I am trying to convert my pytorch model into tensorflow model to run with tensorflowJS. I used below code to convert onnx model to tensorflow model-</p>
  <pre><code>import onnx
  from onnx_tf.backend import prepare
   
  onnx_model = onnx.load(&quot;../input/onnx-model/model.onnx&quot;)
  tf_rep = prepare(onnx_model)
  tf_rep.export_graph(&quot;output/model.pb&quot;)
  </code></pre>
  <p>I got</p>
  <pre><code>SchemaError: No schema registered for 'BitShift'!
  </code></pre>
  <p>I tried with onnx version 1.8.1 , 1.8.0 and then further downgrade to 1.6.0 .</p>
  <p>Also, I tried to run onnx model directly with onnx.js but facing issue in image normalization and resizing. Hence, I decided to switch to tfjs.</p>