Because, input symbol is not created with dtype.
```python
>>> data = mx.sym.var('data')
>>> data.infer_type()
(None, None, None)
```
```python
>>> data = mx.sym.var('data', dtype='float32')
>>> data.infer_type()
([<class 'numpy.float32'>], [<class 'numpy.float32'>], [])
```[ Full content available at: https://github.com/apache/incubator-mxnet/pull/12412 ] This message was relayed via gitbox.apache.org for [email protected]
