Function lightgbm_sys::LGBM_BoosterGetNumClasses

pub unsafe extern "C" fn LGBM_BoosterGetNumClasses(
    handle: BoosterHandle, 
    out_len: *mut c_int
) -> c_int

\brief Get number of classes. \param handle Handle of booster \param[out] out_len Number of classes \return 0 when succeed, -1 when failure happens