Not documented

[GusakIurii]

Can you please tell me where you can find the purpose of these inputs and outputs?
const int IN1 = 16; // input 1 - high active
const int IN2 = 17; // input 2- high active
const int OUT1 = 20; // output 1 - high active
const int OUT2 = 21; // output 1 - high active
const int OUT3 = 22; // output 1 - high active
const int OUT4 = 23; // output 1 - high active
const int OUT5 = 3; // output 1 - high active
const int OUT6 = 4; // output 1 - high active
const int FUEL = 5; // PWM signal of the fuel level sensor

Maybe there is an electrical circuit somewhere?