code: def eth_getCode(self, address, block=BLOCK_TAG_LATEST):
          
          block = validate_block(block)
          return (yield from self.rpc_call('eth_getCode', [address, block]))
docs: https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getcode
  
          :param address: Address of contract
          :type address: str
  
          :param block: Block tag or number (optional)
          :type block: int or BLOCK_TAGS
  
          :return: code
          :rtype: str