Resolve comments

Author: wangxf123456

include/pybind11/cast.h

@@ -435,7 +435,7 @@ struct string_caster {
         auto nbytes = ssize_t(src.size() * sizeof(CharT));
         handle s;
         if (policy == return_value_policy::return_as_bytes) {
-            s = PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, nbytes);
+            s = PyBytes_FromStringAndSize(buffer, nbytes);
         } else {
             s = decode_utfN(buffer, nbytes);
         }

include/pybind11/detail/common.h

@@ -461,11 +461,13 @@ enum class return_value_policy : uint8_t {
         return_value_policy::reference and the keep_alive call policy */
     reference_internal,
 
-    /** Use this policy to make C++ functions return bytes to Python instead of
-        str. This is useful when C++ function returns nested type of string,
-        where we cannot apply `py::bytes` easily. Note that when C++ function
-        returns string, we don't have to deal ownership for sure, because we
-        are always copying the C++ string to a new Python str/bytes object.*/
+    /** With this policy, C++ string types are converted to Python bytes,
+        instead of str. This is most useful when a C++ function returns a
+        container-like type with nested C++ string types, and py::bytes cannot
+        be applied easily. Note that this return_value_policy is not concerned
+        with lifetime/ownership semantics, like the other policies, but the
+        purpose of return_as_bytes is certain to be orthogonal, because C++
+        strings are always copied to Python bytes or str. */
     return_as_bytes
 };