ii-research-yu

def lightgbm_custom_obj_lambdarank(preds, train_data, first_order=False, constant_hessian=1.0):
    '''
    :param preds:      numpy.ndarray of shape (size_data, )
    :param train_data:
    :return:
    '''
    all_labels = train_data.get_label()  # numpy.ndarray of shape (size_data, )
    group = train_data.get_group()       # numpy.ndarray of shape (num_queries, )

    size_data = len(all_labels)