Changed format_string doc string to have accurate parameters and para…

…meter descriptions

python/pyspark/sql/functions.py

@@ -1569,8 +1569,9 @@ def format_string(format, *cols):
     """
     Formats the arguments in printf-style and returns the result as a string column.
 
-    :param col: the column name of the numeric value to be formatted
-    :param d: the N decimal places
+    :param format: string that can contain embedded format tags and used as result column's value
+    :param cols: list of column names (string) or list of :class:`Column` expressions to
+        be used in formatting
 
     >>> df = spark.createDataFrame([(5, "hello")], ['a', 'b'])
     >>> df.select(format_string('%d %s', df.a, df.b).alias('v')).collect()