question about static schema in a model

gistfile1.txt

    // // find by token
    // userSchema.statics.findByToken = function(token,cb){
    //     var user = this;
    //     var SECRET= process.env.SECRET;
    //     jwt.verify(token,SECRET,function(err,decode){
    //         user.findone({"_id": decode, "token":token},function(err,user){
    //             if(err) return cb(err);
    //             cb(null,user);

    //         })
    //     })
    // };
userSchema.methods.generateAuthToken = async function() {
    // Generate an auth token for the user
    const user = this
    const token = jwt.sign({_id: user._id}, process.env.SECRET)
    user.tokens = user.tokens.concat({token})
    await user.save()
    return token
}

// userSchema.statics.findByCredentials = async (email, password) => {
//     // Search for a user by email and password.
//     const user = await User.findOne({ email} )
//     if (!user) {
//         throw new Error({ error: 'Invalid login credentials' })
//     }
//     const isPasswordMatch = await bcrypt.compare(password, user.password)
//     if (!isPasswordMatch) {
//         throw new Error({ error: 'Invalid login credentials' })
//     }
//     return user
// }