def createTransactionLookupConnector(chain=Chain.bitcoin_mainnet, options=None):
if chain == Chain.mockchain or chain == Chain.bitcoin_regtest:<EOL><INDENT>return MockConnector(chain)<EOL><DEDENT>elif chain.blockchain_type == BlockchainType.ethereum:<EOL><INDENT>if options and '<STR_LIT>' in options:<EOL><INDENT>etherscan_api_token = options['<STR_LIT>']<EOL><DEDENT>else:<EOL><INDENT>etherscan_api_token = '<STR_LIT>'<EOL><DEDENT>return EtherscanConnector(chain, etherscan_api_token)<EOL><DEDENT>return FallbackConnector(chain)<EOL>
:param chain: which chain, supported values are testnet and mainnet
:return: connector for looking up transactions