function totalSupply() external view returns (uint256);
function balanceOf(address who) external view returns (uint256);
function estimateFee(uint256 value) external view returns (uint256);
function issuer() external view returns (address);
function allowance(address owner, address spender) external view returns (uint256);
function transfer(address to, uint256 value) external returns (bool);
function approve(address spender, uint256 value) external returns (bool);
function transferFrom(address from, address to, uint256 value) external returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);
event Fee(address indexed from, address indexed to, address indexed issuer, uint256 value);