CLN: move import to top of file

For consistency with [PEP8][1]:

    Imports are always put at the top of the file, just after any module
    comments and docstrings, and before module globals and constants.

[1]: https://www.python.org/dev/peps/pep-0008#id17

Author: aevri

pandas/core/config.py

@@ -51,6 +51,7 @@
 import re
 
 from collections import namedtuple
+from contextlib import contextmanager
 import warnings
 from pandas.compat import map, lmap, u
 import pandas.compat as compat
@@ -681,8 +682,6 @@ def pp(name, ks):
 #
 # helpers
 
-from contextlib import contextmanager
-
 
 @contextmanager
 def config_prefix(prefix):