pylint, do not use -1 for default value

python/tvm/relay/op/_transform.py

@@ -1102,10 +1102,6 @@ def gather_nd_shape_func(attrs, inputs, _):
     batch_dims = get_const_int(attrs.batch_dims)
     index_rank = get_const_int(attrs.index_rank)
 
-    assert (
-        index_rank > 0
-    ), "index_rank needs to be specified for dynamic gather_nd"
+    assert index_rank > 0, "index_rank needs to be specified for dynamic gather_nd"
 
-    return [
-        _gather_nd_shape(inputs[0], inputs[1], convert(batch_dims), convert(index_rank))
-    ]
+    return [_gather_nd_shape(inputs[0], inputs[1], convert(batch_dims), convert(index_rank))]

python/tvm/relay/op/transform.py

@@ -1072,7 +1072,7 @@ def gather(data, axis, indices):
     return _make.gather(data, axis, indices)
 
 
-def gather_nd(data, indices, batch_dims=0, index_rank=-1):
+def gather_nd(data, indices, batch_dims=0, index_rank=None):
     """Gather elements or slices from data and store to a tensor whose shape is
     defined by indices.
 
@@ -1087,7 +1087,7 @@ def gather_nd(data, indices, batch_dims=0, index_rank=-1):
     batch_dims : int
         The number of batch dimensions.
 
-    index_rank : int
+    index_rank : int, optional
         The size of an indexing tuple, which is a fixed value and the same as indices.shape[0]
         Only needed when other dimensions of indices are dynamic.
 

src/relay/op/tensor/transform.cc

@@ -3373,11 +3373,12 @@ Array<te::Tensor> GatherNDCompute(const Attrs& attrs, const Array<te::Tensor>& i
   return {topi::gather_nd(inputs[0], inputs[1], param->batch_dims)};
 }
 
-Expr MakeGatherND(Expr data, Expr indices, int batch_dims = 0, int index_rank = -1) {
+Expr MakeGatherND(Expr data, Expr indices, int batch_dims = 0,
+                  Optional<Integer> index_rank = NullValue<Integer>()) {
   static const Op& op = Op::Get("gather_nd");
   auto attrs = make_object<GatherNDAttrs>();
   attrs->batch_dims = batch_dims;
-  attrs->index_rank = Integer(index_rank);
+  attrs->index_rank = index_rank;
   return Call(op, {data, indices}, Attrs(attrs));
 }