Problem how to write a coding for current sensor GY-712

the coding that i have obtained was definitely for simple value of current..the value current that i want to obtained maybe until microampere or nanoampere. this is because my project is to detect the value of current in engine oil/libricant..since the value mentioned from the journal was in micro until nano n below. so my question is how to write a coding for sensor GY-712 to detect the value of current mentioned above. tq so much