DOC: fix namespace

Author: jorisvandenbossche

doc/source/basics.rst

@@ -1503,9 +1503,9 @@ faster than sorting the entire Series and calling ``head(n)`` on the result.
 
 .. ipython:: python
 
-   df = DataFrame({'a': [-2, -1, 1, 10, 8, 11, -1],
-                   'b': list('abdceff'),
-                   'c': [1.0, 2.0, 4.0, 3.2, np.nan, 3.0, 4.0]})
+   df = pd.DataFrame({'a': [-2, -1, 1, 10, 8, 11, -1],
+                      'b': list('abdceff'),
+                      'c': [1.0, 2.0, 4.0, 3.2, np.nan, 3.0, 4.0]})
    df.nlargest(3, 'a')
    df.nlargest(5, ['a', 'c'])
    df.nsmallest(3, 'a')