Minor code and comment cleanup (GH-16315) (GH-16316)

(cherry picked from commit 7ce4bfa)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>

Author: miss-islington

Lib/statistics.py

@@ -555,8 +555,9 @@ def mode(data):
 
     """
     data = iter(data)
+    pairs = Counter(data).most_common(1)
     try:
-        return Counter(data).most_common(1)[0][0]
+        return pairs[0][0]
     except IndexError:
         raise StatisticsError('no mode for empty data') from None
 
@@ -602,6 +603,7 @@ def multimode(data):
 # mean=0.300.  Only the latter (which corresponds with R6) gives the
 # desired cut point with 30% of the population falling below that
 # value, making it comparable to a result from an inv_cdf() function.
+# The R6 exclusive method is also idempotent.
 
 # For describing population data where the end points are known to
 # be included in the data, the R7 inclusive method is a reasonable