gradient tolerance and alpha

[wangjiawen2013]

Hi,
who can kindly tell the meaning of "gradient_tolerance" and "alpha" parameters ? what's the default value for them ? which one is the learning rate ? I cannot not find the usage from linfa-logistic documentation.

let model = LogisticRegression::default()
        .max_iterations(max_iterations)
        .gradient_tolerance(0.0001)
        .alpha(0.001)
        .fit(&train)
        .expect("Cannot train model");