Closes #20872: dbm/gdbm/ndbm close methods are not documented

Doc/library/dbm.rst

@@ -216,6 +216,9 @@ supported.
       When the database has been opened in fast mode, this method forces any
       unwritten data to be written to the disk.
 
+   .. method:: gdbm.close()
+
+      Close the ``gdbm`` database.
 
 :mod:`dbm.ndbm` --- Interface based on ndbm
 -------------------------------------------
@@ -247,7 +250,7 @@ to locate the appropriate header file to simplify building this module.
 
 .. function:: open(filename[, flag[, mode]])
 
-   Open a dbm database and return a ``dbm`` object.  The *filename* argument is the
+   Open a dbm database and return a ``ndbm`` object.  The *filename* argument is the
    name of the database file (without the :file:`.dir` or :file:`.pag` extensions).
 
    The optional *flag* argument must be one of these values:
@@ -272,6 +275,12 @@ to locate the appropriate header file to simplify building this module.
    database has to be created.  It defaults to octal ``0o666`` (and will be
    modified by the prevailing umask).
 
+   In addition to the dictionary-like methods, ``ndbm`` objects
+   provide the following method:
+
+   .. method:: ndbm.close()
+
+      Close the ``ndbm`` database.
 
 
 :mod:`dbm.dumb` --- Portable DBM implementation
@@ -319,9 +328,14 @@ The module defines the following:
 
    In addition to the methods provided by the
    :class:`collections.abc.MutableMapping` class, :class:`dumbdbm` objects
-   provide the following method:
+   provide the following methods:
 
    .. method:: dumbdbm.sync()
 
       Synchronize the on-disk directory and data files.  This method is called
       by the :meth:`Shelve.sync` method.
+
+   .. method:: dumbdbm.close()
+
+      Close the ``dumbdbm`` database.
+