[TensorRT, BYOC] Handling a corner case in TRT RemoveDropout pass

[rohanmukh]

This commit handles a corner case in TRT RemoveDropout pass. This avoids an error like below

File "/home/ubuntu/workspace/tvm/python/tvm/runtime/object.py", line 65, in __getattr__
    raise AttributeError("%s has no attribute %s" % (str(type(self)), name))
AttributeError: relay.Let object has no attributed name
During handling of the above exception, another exception occurred:
AttributeError: <class 'tvm.relay.expr.Let'> has no attribute name 

[rohanmukh]

@trevor-m @comaniac

[comaniac]

This looks a bit ad-hoc to me. Suggest as follows. Note that I'm not sure if isinstance(visit.tuple_value.op, Op) is the correct expression but you should know what I meant.

if isinstance(visit.tuple_value, Call):
  if isinstance(visit.tuple_value.op, Op) and visit.tuple_value.op.name == "nn.dropout" and visit.index == 0:
    return visit.tuple_value.args[0]
return visit

[rohanmukh]

Thanks @comaniac . Changed the logic as appropriate.

[comaniac]

LGTM