code: def isunique(table, field):
      
  
      vals = set()
      for v in itervalues(table, field):
          if v in vals:
              return False
          else:
              vals.add(v)
      return True
docs: Return True if there are no duplicate values for the given field(s),
      otherwise False. E.g.::
  
          >>> import petl as etl
          >>> table1 = [['foo', 'bar'],
          ...           ['a', 1],
          ...           ['b'],
          ...           ['b', 2],
          ...           ['c', 3, True]]
          >>> etl.isunique(table1, 'foo')
          False
          >>> etl.isunique(table1, 'bar')
          True
  
      The `field` argument can be a single field name or index (starting from
      zero) or a tuple of field names and/or indexes.