Improve appearance of example code

Doc/library/collections.rst

@@ -905,15 +905,15 @@ functionality with a subclass.  Here is how to add a calculated field and
 a fixed-width print format:
 
     >>> class Point(namedtuple('Point', 'x y')):
-        __slots__ = ()
-        @property
-        def hypot(self):
-            return (self.x ** 2 + self.y ** 2) ** 0.5
-        def __str__(self):
-            return 'Point: x=%6.3f  y=%6.3f  hypot=%6.3f' % (self.x, self.y, self.hypot)
+            __slots__ = ()
+            @property
+            def hypot(self):
+                return (self.x ** 2 + self.y ** 2) ** 0.5
+            def __str__(self):
+                return 'Point: x=%6.3f  y=%6.3f  hypot=%6.3f' % (self.x, self.y, self.hypot)
 
     >>> for p in Point(3, 4), Point(14, 5/7):
-        print(p)
+            print(p)
     Point: x= 3.000  y= 4.000  hypot= 5.000
     Point: x=14.000  y= 0.714  hypot=14.018