Minor fix to SPARK-6958: Improve Python docstring for DataFrame.sort.

As a follow up PR to apache#5544.

cc davies

Author: Reynold Xin <[email protected]>

Closes apache#5558 from rxin/sort-doc-improvement and squashes the following commits:

f4c276f [Reynold Xin] Review feedback.
d2dcf24 [Reynold Xin] Minor fix to SPARK-6958: Improve Python docstring for DataFrame.sort.

Author: rxin

python/pyspark/sql/dataframe.py

@@ -489,8 +489,9 @@ def sort(self, *cols, **kwargs):
         """Returns a new :class:`DataFrame` sorted by the specified column(s).
 
         :param cols: list of :class:`Column` or column names to sort by.
-        :param ascending: sort by ascending order or not, could be bool, int
-             or list of bool, int (default: True).
+        :param ascending: boolean or list of boolean (default True).
+            Sort ascending vs. descending. Specify list for multiple sort orders.
+            If a list is specified, length of the list must equal length of the `cols`.
 
         >>> df.sort(df.age.desc()).collect()
         [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
@@ -519,7 +520,7 @@ def sort(self, *cols, **kwargs):
             jcols = [jc if asc else jc.desc()
                      for asc, jc in zip(ascending, jcols)]
         else:
-            raise TypeError("ascending can only be bool or list, but got %s" % type(ascending))
+            raise TypeError("ascending can only be boolean or list, but got %s" % type(ascending))
 
         jdf = self._jdf.sort(self._jseq(jcols))
         return DataFrame(jdf, self.sql_ctx)