code: def _blockedPairs(self, blocks):
          
  
          block, blocks = core.peek(blocks)
          self._checkBlock(block)
  
          combinations = itertools.combinations
  
          pairs = (combinations(sorted(block), 2) for block in blocks)
  
          return pairs
docs: Generate tuples of pairs of records from a block of records
  
          Arguments:
  
          blocks -- an iterable sequence of blocked records