Issue #23921: Standardized documentation whitespace formatting.

Original patch by James Edwards.

Doc/reference/datamodel.rst

@@ -1754,11 +1754,11 @@ to remember the order that class variables are defined::
 
     class OrderedClass(type):
 
-         @classmethod
-         def __prepare__(metacls, name, bases, **kwds):
+        @classmethod
+        def __prepare__(metacls, name, bases, **kwds):
             return collections.OrderedDict()
 
-         def __new__(cls, name, bases, namespace, **kwds):
+        def __new__(cls, name, bases, namespace, **kwds):
             result = type.__new__(cls, name, bases, dict(namespace))
             result.members = tuple(namespace)
             return result

Doc/reference/expressions.rst

@@ -728,7 +728,7 @@ A consequence of this is that although the ``*expression`` syntax may appear
 (and the ``**expression`` argument, if any -- see below).  So::
 
    >>> def f(a, b):
-   ...  print(a, b)
+   ...     print(a, b)
    ...
    >>> f(b=1, *(2,))
    2 1

Doc/reference/simple_stmts.rst

@@ -331,12 +331,12 @@ program:
 The simple form, ``assert expression``, is equivalent to ::
 
    if __debug__:
-      if not expression: raise AssertionError
+       if not expression: raise AssertionError
 
 The extended form, ``assert expression1, expression2``, is equivalent to ::
 
    if __debug__:
-      if not expression1: raise AssertionError(expression2)
+       if not expression1: raise AssertionError(expression2)
 
 .. index::
    single: __debug__