DOC: Correct documentation to GroupBy.rank

Closes pandas-devgh-20694.

Author: gfyoung

pandas/core/groupby/groupby.py

@@ -1841,24 +1841,27 @@ def cumcount(self, ascending=True):
     @Appender(_doc_template)
     def rank(self, method='average', ascending=True, na_option='keep',
              pct=False, axis=0):
-        """Provides the rank of values within each group
+        """
+        Provides the rank of values within each group.
 
         Parameters
         ----------
-        method : {'average', 'min', 'max', 'first', 'dense'}, efault 'average'
+        method : {'average', 'min', 'max', 'first', 'dense'}, default 'average'
             * average: average rank of group
             * min: lowest rank in group
             * max: highest rank in group
             * first: ranks assigned in order they appear in the array
             * dense: like 'min', but rank always increases by 1 between groups
-        method :  {'keep', 'top', 'bottom'}, default 'keep'
+        ascending : boolean, default True
+            False for ranks by high (1) to low (N)
+        na_option :  {'keep', 'top', 'bottom'}, default 'keep'
             * keep: leave NA values where they are
             * top: smallest rank if ascending
             * bottom: smallest rank if descending
-        ascending : boolean, default True
-            False for ranks by high (1) to low (N)
         pct : boolean, default False
             Compute percentage rank of data within each group
+        axis : int, default 0
+            The axis of the object over which to compute the rank.
 
         Returns
         -----