solidity chainid test for istanbul migration

TestChainID.sol

pragma solidity ^0.5.13;

contract TestChainID {
  function getChainID() external pure returns (uint256) {
    uint256 id;
    assembly {
      id := chainid()
    }
    return id;
  }
}

/*
Available options in parity chain file:
one of `accountStartNonce`, `maximumExtraDataSize`, `minGasLimit`, `networkID`, `chainID`, `subprotocolName`, `forkBlock`, `forkCanonHash`, `eip150Transition`, `eip160Transition`, `eip161abcTransition`, `eip161dTransition`, `eip98Transition`, `eip155Transition`, `validateChainIdTransition`, `validateReceiptsTransition`, `eip140Transition`, `eip210Transition`, `eip210ContractAddress`, `eip210ContractCode`, `eip210ContractGas`, `eip211Transition`, `eip145Transition`, `eip214Transition`, `eip658Transition`, `eip1052Transition`, `eip1283Transition`, `eip1283DisableTransition`, `eip1283ReenableTransition`, `eip1014Transition`, `eip1706Transition`, `eip1344Transition`, `eip1884Transition`, `eip2028Transition`, `dustProtectionTransition`, `nonceCapIncrement`, `removeDustContracts`, `gasLimitBoundDivisor`, `registrar`, `applyReward`, `nodePermissionContract`, `maxCodeSize`, `maxTransactionSize`, `maxCodeSizeTransition`, `transactionPermissionContract`, `transactionPermissionContractTransition`, `wasmActivationTransition`, `kip4Transition`, `kip6Transition`
*/