code: def rowlengths(table):
      
  
      counter = Counter()
      for row in data(table):
          counter[len(row)] += 1
      output = [('length', 'count')]
      output.extend(counter.most_common())
      return wrap(output)
docs: Report on row lengths found in the table. E.g.::
  
          >>> import petl as etl
          >>> table = [['foo', 'bar', 'baz'],
          ...          ['A', 1, 2],
          ...          ['B', '2', '3.4'],
          ...          [u'B', u'3', u'7.8', True],
          ...          ['D', 'xyz', 9.0],
          ...          ['E', None],
          ...          ['F', 9]]
          >>> etl.rowlengths(table)
          +--------+-------+
          | length | count |
          +========+=======+
          |      3 |     3 |
          +--------+-------+
          |      2 |     2 |
          +--------+-------+
          |      4 |     1 |
          +--------+-------+
  
      Useful for finding potential problems in data files.