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

Doc/library/anydbm.rst

@@ -92,6 +92,14 @@ then prints out the contents of the database::
    db.close()
 
 
+In addition to the dictionary-like methods, ``anydbm`` objects
+provide the following method:
+
+.. function:: close()
+
+   Close the ``anydbm`` database.
+
+
 .. seealso::
 
    Module :mod:`dbhash`

Doc/library/dbm.rst

@@ -64,6 +64,14 @@ The module defines the following:
    database has to be created.  It defaults to octal ``0666`` (and will be
    modified by the prevailing umask).
 
+   In addition to the dictionary-like methods, ``dbm`` objects
+   provide the following method:
+
+
+   .. function:: close()
+
+      Close the ``dbm`` database.
+
 
 .. seealso::
 

Doc/library/dumbdbm.rst

@@ -49,6 +49,14 @@ The module defines the following:
    .. versionchanged:: 2.2
       The *mode* argument was ignored in earlier versions.
 
+In addition to the dictionary-like methods, ``dumbdm`` objects
+provide the following method:
+
+
+.. function:: close()
+
+   Close the ``dumbdm`` database.
+
 
 .. seealso::
 

Doc/library/gdbm.rst

@@ -116,6 +116,11 @@ methods:
    unwritten data to be written to the disk.
 
 
+.. function:: close()
+
+   Close the ``gdbm`` database.
+
+
 .. seealso::
 
    Module :mod:`anydbm`