Update GetInputTensorType and GetOutputTensorType methods in litert_model.h to use the Signature class's InputTensor and OutputTensor methods

LiteRT-PiperOrigin-RevId: 820780454

Author: ai-edge-bot

litert/cc/litert_model.h

@@ -532,15 +532,19 @@ class Model : public internal::Handle<LiteRtModel, LiteRtDestroyModel> {
   // Returns the tensor type for the given n-th input tensor.
   Expected<RankedTensorType> GetInputTensorType(size_t signature_index,
                                                 size_t input_index) const {
-    LITERT_ASSIGN_OR_RETURN(auto subgraph, Subgraph(signature_index));
-    return subgraph.Inputs()[input_index].RankedTensorType();
+    LITERT_ASSIGN_OR_RETURN(const Signature& signature,
+                            GetSignature(signature_index));
+    LITERT_ASSIGN_OR_RETURN(const Tensor& tensor,
+                            signature.InputTensor(input_index));
+    return tensor.RankedTensorType();
   }
 
   // Returns the tensor type for the given input tensor name.
   Expected<RankedTensorType> GetInputTensorType(
       size_t signature_index, absl::string_view input_name) const {
-    LITERT_ASSIGN_OR_RETURN(auto subgraph, Subgraph(signature_index));
-    LITERT_ASSIGN_OR_RETURN(auto tensor, subgraph.Input(input_name));
+    LITERT_ASSIGN_OR_RETURN(const Signature& signature,
+                            GetSignature(signature_index));
+    LITERT_ASSIGN_OR_RETURN(auto tensor, signature.InputTensor(input_name));
     return tensor.RankedTensorType();
   }
 
@@ -553,15 +557,19 @@ class Model : public internal::Handle<LiteRtModel, LiteRtDestroyModel> {
   // Returns the tensor type for the given n-th output tensor.
   Expected<RankedTensorType> GetOutputTensorType(size_t signature_index,
                                                  size_t output_index) const {
-    auto subgraph = Subgraph(signature_index);
-    return subgraph->Outputs()[output_index].RankedTensorType();
+    LITERT_ASSIGN_OR_RETURN(const Signature& signature,
+                            GetSignature(signature_index));
+    LITERT_ASSIGN_OR_RETURN(const Tensor& tensor,
+                            signature.OutputTensor(output_index));
+    return tensor.RankedTensorType();
   }
 
   // Returns the tensor type for the given output tensor name.
   Expected<RankedTensorType> GetOutputTensorType(
       size_t signature_index, absl::string_view output_name) const {
-    auto subgraph = Subgraph(signature_index);
-    LITERT_ASSIGN_OR_RETURN(auto tensor, subgraph->Output(output_name));
+    LITERT_ASSIGN_OR_RETURN(const Signature& signature,
+                            GetSignature(signature_index));
+    LITERT_ASSIGN_OR_RETURN(auto tensor, signature.OutputTensor(output_name));
     return tensor.RankedTensorType();
   }