Function py_classify_ode 

pub fn py_classify_ode(
    equation: &Expression,
    func: &str,
    var: &str,
) -> PyResult<Vec<String>>

Classify an ODE and return the applicable method names.

equation is the ODE written as an expression equal to zero (e.g. "Derivative(y(x), x) - y(x)"), func the unknown function name (e.g. "y"), and var the independent variable (e.g. "x").

Returns a list of method names such as "LinearFirst", "Separable", "LinearConstantCoeff", etc.