gh-137533: document key type coercion limitations in json.loads

Doc/library/json.rst

@@ -146,6 +146,11 @@ See :ref:`json-commandline` for detailed documentation.
    This module's encoders and decoders preserve input and output order by
    default.  Order is only lost if the underlying containers are unordered.
 
+.. note::
+   :rfc:`7159` requires that keys in key/value pairs of JSON are always of the
+   type :class:`str`. When a dictionary is converted into JSON, all the keys
+   of the dictionary arecoerced to strings.When a JSON object is converted into
+   dictionaries,all the keys of the dictionary are strings.
 
 Basic Usage
 -----------
@@ -256,12 +261,10 @@ Basic Usage
 
    .. note::
 
-      Keys in key/value pairs of JSON are always of the type :class:`str`. When
-      a dictionary is converted into JSON, all the keys of the dictionary are
-      coerced to strings. As a result of this, if a dictionary is converted
-      into JSON and then back into a dictionary, the dictionary may not equal
-      the original one. That is, ``loads(dumps(x)) != x`` if x has non-string
-      keys.
+      The encoder will convert all non-string keys in dictionaries into string,
+      if a dictionary is converted into JSON and then back into a dictionary,
+      the dictionary may not equal the original one.
+      That is, ``loads(dumps(x)) != x`` if x has non-string keys.
 
 .. function:: load(fp, *, cls=None, object_hook=None, parse_float=None, \
                    parse_int=None, parse_constant=None, \
@@ -364,6 +367,11 @@ Basic Usage
    .. versionchanged:: 3.9
       The keyword argument *encoding* has been removed.
 
+   .. note::
+
+      The decoder will convert all JSON objects' keys into string as
+      the key of dictionaries,for example,
+      ``json.loads('{"spam":"foo"}')`` returns ``{'spam':'foo'}``
 
 Encoders and Decoders
 ---------------------