code: def get_confirmed_blockhash(self):
          
          confirmed_block_number = self.web3.eth.blockNumber - self.default_block_num_confirmations
          if confirmed_block_number < 0:
              confirmed_block_number = 0
  
          return self.blockhash_from_blocknumber(confirmed_block_number)
docs: Gets the block CONFIRMATION_BLOCKS in the past and returns its block hash