Ηow to compute the Asymptotic complexity (big O) of machine learning algorithms

Hello everyone,

I hope this message finds you all well.
In a task assigned to me, I was asked to calculate Asymptotic complexity (big O) of machine learning algorithms that i used .

Does anyone know if I can get this from an operator. 
In case it does not exist, do you know valid bibliography that I can search

Thank you in advance