Callback is not a function NODEJS - callback

Question

I am trying learn nodejs and stumble upon this error
callback(null, removed);
TypeError: callback is not a function
It is a Steam trade bot, so when it send me an offer, I accept it but after that it crashes. What is wrong?
exports.removeOweNoTitle = (user, callback) => {
let file = 'data/users/' + user + '.json';
if(fs.existsSync(file)) {
let read = fs.createReadStream(file);
let data = "";
read.on('data', (chunk) => {
data += chunk;
});
read.on('end', () => {
let json;
try {
json = JSON.parse(data);
} catch(error) {
return callback(error);
}
let owe = {};
if(json.owe)
owe = json.owe;
else {
callback(null, 0);
return;
}
let removed = 0;
for(let game in owe) {
if(owe[game]) {
removed += owe[game];
owe[game] = 0;
}
}
let write = fs.createWriteStream(file, {flags: 'w'});
exports.clearNotifications(user, () => {
write.write(JSON.stringify(json), (error) => {
if(error)
return callback(error);
write.end();
});
return;
});
write.write(JSON.stringify(json), (error) => {
if(error)
return callback(error);
write.end();
});
write.on("finish", (callback, error) => {
callback(null, removed); //tady nebyl deklarován callback chyběl
});
});
} else {
generateUserFile(user);
callback(new Error('User\'s file is not defined!'), null);
}
}