Close #15387: inspect.getmodulename() now uses a new importlib.machinery.all_suffixes() API rather than the deprecated inspect.getmoduleinfo()
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index cea2da0..daf9e56 100644
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -533,12 +533,23 @@
 
 .. attribute:: EXTENSION_SUFFIXES
 
-   A list of strings representing the the recognized file suffixes for
+   A list of strings representing the recognized file suffixes for
    extension modules.
 
    .. versionadded:: 3.3
 
 
+.. func:: all_suffixes()
+
+   Returns a combined list of strings representing all file suffixes for
+   Python modules recognized by the standard import machinery. This is a
+   helper for code which simply needs to know if a filesystem path
+   potentially represents a Python module (for example,
+   :func:`inspect.getmodulename`)
+
+   .. versionadded:: 3.3
+
+
 .. class:: BuiltinImporter
 
     An :term:`importer` for built-in modules. All known built-in modules are