Update docs

pandas/core/series.py

@@ -1422,7 +1422,7 @@ def to_string(self, buf=None, na_rep='NaN', float_format=None, header=True,
  Returns
  -------
  str or None
- String representation of Series if buf=None, otherwise None.
+ String representation of Series if ``buf=None``, otherwise None.
  """
 
  formatter = fmt.SeriesFormatter(self, name=name, length=length,
@@ -3012,7 +3012,9 @@ def argsort(self, axis=0, kind='quicksort', order=None):
 
  Returns
  -------
- Series, with -1 indicated where nan values are present
+ Series
+ Positions of values within the sort order with -1 indicating
+ nan values.
 
  See Also
  --------