[Quantization] Problems with recent refactoring changes in the quantization pass

Troubleshooting
1

Hi,

After the last changes in the quantization in the following commit, I am facing some issues:

  1. I get the following error:
  File "/home/tvm/tvm/python/tvm/relay/quantize/_partition.py", line 136, in add_partition_function
    if 'cuda' in _target.current_target().keys:
AttributeError: 'NoneType' object has no attribute 'keys'
  1. If I remove the problematic code in 1, the accuracy of a quantized model, which was previously working, drops to the point that the output of the model is not valid anymore.

@vinx13 can you have a look into this? I saw that the mentioned commit touches some aspects of accuracy.

Thanks