Add tutorial section about coding style.
diff --git a/Doc/tutorial/introduction.rst b/Doc/tutorial/introduction.rst
index 3bbe53a..5e027a0 100644
--- a/Doc/tutorial/introduction.rst
+++ b/Doc/tutorial/introduction.rst
@@ -578,8 +578,8 @@
    ... # the sum of two elements defines the next
    ... a, b = 0, 1
    >>> while b < 10:
-   ...       print b
-   ...       a, b = b, a+b
+   ...     print b
+   ...     a, b = b, a+b
    ... 
    1
    1