Function lightgbm_sys::LGBM_BoosterGetNumPredict

pub unsafe extern "C" fn LGBM_BoosterGetNumPredict(
    handle: BoosterHandle, 
    data_idx: c_int, 
    out_len: *mut i64
) -> c_int

\brief Get number of predictions for training data and validation data (this can be used to support customized evaluation functions). \param handle Handle of booster \param data_idx Index of data, 0: training data, 1: 1st validation data, 2: 2nd validation data and so on \param[out] out_len Number of predictions \return 0 when succeed, -1 when failure happens