Add line to separate examples.

Author: eric

doc/source/io.rst

@@ -135,7 +135,8 @@ usecols : array-like or callable, default ``None``
   be positional (i.e. integer indices into the document columns) or strings
   that correspond to column names provided either by the user in `names` or
   inferred from the document header row(s). For example, a valid array-like
-  `usecols` parameter would be ``[0, 1, 2]`` or ``['foo', 'bar', 'baz']``. 
+  `usecols` parameter would be ``[0, 1, 2]`` or ``['foo', 'bar', 'baz']``.
+
   Element order is ignored, so ``usecols=[0, 1]`` is the same as ``[1, 0]``. To
   instantiate a DataFrame from ``data`` with element order preserved use
   ``pd.read_csv(data, usecols=['foo', 'bar'])[['foo', 'bar']]`` for columns