code: def eth_getBlockTransactionCountByNumber(self, block=BLOCK_TAG_LATEST):
          
          block = validate_block(block)
          return hex_to_dec((yield from self.rpc_call('eth_getBlockTransactionCountByNumber',
                                                      [block])))
docs: https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getblocktransactioncountbynumber
  
          :param block: Block tag or number (optional)
          :type block: int or BLOCK_TAGS
  
          :return: count
          :rtype: int