message: new: tokenOfOwnerByIndex() implementation
diff: @@ -43,4 +43,28 @@ export class ERC721 extends BaseToken {
  });
  }
  + /**
  + * READ
  + * returns token's id on that index
  + *
  + * @param userAddress
  + * @param index starting from zero, if no token found on that it will return error
  + * @param option
  + */
  + tokenOfOwnerByIndexERC721(userAddress: string, index: number, option: ITransactionOption = {}) {
  + const contract = this.contract;
  + const method = contract.method(
  + "tokenOfOwnerByIndex",
  + userAddress,
  + index
  + );
  +
  + return createTransactionConfig(
  + {
  + txConfig: {},
  + defaultTxConfig: this.childDefaultConfig,
  + }).then(config => {
  + return method.read<string>(config);
  + });
  + }
  }
  