code: def most_common(self, n=None):
          '''List the n most common elements and their counts from the most
          common to the least.  If n is None, then list all element counts.
  
          >>> Counter('abracadabra').most_common(3)
          [('a', 5), ('r', 2), ('b', 2)]
  
          '''
          if n is None:
              return sorted(iteritems(self), key=itemgetter(1), reverse=True)
          return nlargest(n, iteritems(self), key=itemgetter(1)f most_common(self, n=None):
          '''List the n most common elements and their counts from the most
          common to the least.  If n is None, then list all element counts.
  
          >>> Counter('abracadabra').most_common(3)
          [('a', 5), ('r', 2), ('b', 2)]
  
          '''
          if n is None:
              return sorted(iteritems(self), key=itemgetter(1), reverse=True)
          return nlargest(n, iteritems(self), key=itemgetter(1))
docs: List the n most common elements and their counts from the most
          common to the least.  If n is None, then list all element counts.
  
          >>> Counter('abracadabra').most_common(3)
          [('a', 5), ('r', 2), ('b', 2)]