TRC10 missing sendToken method implementation

TRC10.sol

library TRC10 {
  using TRC10 for address;

  function sendToken(address to, uint256 tokenid, uint256 amount) internal returns(bool) {
    return this.call(abi.encodeWithSelector(this._transferToken.selector, to, tokenid, amount));
  }

  function _transferToken(address to, uint256 tokenid, uint256 amount) private {
    to.transferToken(tokenid, amount);
  }
}