code: def namedb_history_extract( history_rows ):
      
  
      history = {}
      for history_row in history_rows:
  
          block_id = history_row['block_id']
          data_json = history_row['history_data']
          hist = json.loads( data_json )
          
          hist['opcode'] = op_get_opcode_name( hist['op'] )
          hist = op_decanonicalize(hist['opcode'], hist)
  
          if history.has_key( block_id ):
              history[ block_id ].append( hist )
          else:
              history[ block_id ] = [ hist ]
  
      return history
docs: Given the rows of history for a name, collapse
      them into a history dictionary.
      Return a dict of:
      {
          block_id: [
              { ... historical copy ...
               txid:
               vtxindex:
               op:
               opcode: 
              }, ...
          ],
          ...
      }