[ExecuTorch][#9638] Introduce Protected Method Getter in Extension.Module (#10384)

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ghstack PR number: #10374 by
@zhenyan-zhang-meta
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ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/zhenyan-zhang-meta/4/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/zhenyan-zhang-meta/4/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/main
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https://github.com/pytorch/executorch/tree/gh/zhenyan-zhang-meta/4/orig
@diff-train-skip-merge

Co-authored-by: zhenyanzhang <[email protected]>

Author: pytorchbot

extension/module/module.cpp

@@ -302,5 +302,15 @@ runtime::Error Module::set_output(
       output_tensor.mutable_data_ptr(), output_tensor.nbytes(), output_index);
 }
 
+ET_NODISCARD inline runtime::Result<Method*> Module::get_method(
+    const std::string& method_name) {
+  ET_CHECK_OR_RETURN_ERROR(
+      methods_.count(method_name) > 0,
+      InvalidArgument,
+      "no such method in program: %s",
+      method_name.c_str());
+  return methods_[method_name].method.get();
+}
+
 } // namespace extension
 } // namespace executorch

extension/module/module.h

@@ -493,6 +493,16 @@ class Module {
   std::unique_ptr<NamedDataMap> data_map_;
 
  protected:
+  /**
+   * Get a method by method name.
+   *
+   * @param[in] method_name The name of the method to get.
+   *
+   * @returns A Result object containing either a pointer to the requested
+   *          method or an error to indicate failure.
+   */
+  ET_NODISCARD inline runtime::Result<Method*> get_method(
+      const std::string& method_name);
   std::unordered_map<std::string, MethodHolder> methods_;
 
   friend class ExecuTorchJni;