Serialize memory_format (pytorch#81332)

Pull Request resolved: pytorch#81332
Approved by: https://github.com/qihqi

Author: angelayi

torch/csrc/MemoryFormat.cpp

@@ -28,6 +28,17 @@ PyObject* THPMemoryFormat_repr(THPMemoryFormat* self) {
   return THPUtils_packString(self->name);
 }
 
+PyObject* THPMemoryFormat_reduce(PyObject* _self, PyObject* noargs) {
+  auto* self = (THPMemoryFormat*)_self;
+  return THPUtils_packString(self->name);
+}
+
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,cppcoreguidelines-avoid-non-const-global-variables,modernize-avoid-c-arrays)
+static PyMethodDef THPMemoryFormat_methods[] = {
+    {"__reduce__", THPMemoryFormat_reduce, METH_NOARGS, nullptr},
+    {nullptr} /* Sentinel */
+};
+
 PyTypeObject THPMemoryFormatType = {
     PyVarObject_HEAD_INIT(nullptr, 0) "torch.memory_format", /* tp_name */
     sizeof(THPMemoryFormat), /* tp_basicsize */
@@ -55,7 +66,7 @@ PyTypeObject THPMemoryFormatType = {
     0, /* tp_weaklistoffset */
     nullptr, /* tp_iter */
     nullptr, /* tp_iternext */
-    nullptr, /* tp_methods */
+    THPMemoryFormat_methods, /* tp_methods */
     nullptr, /* tp_members */
     nullptr, /* tp_getset */
     nullptr, /* tp_base */