Calculates gains for each feature and returns the best possible split information for the feature.

The split information is the best threshold (bucket id), gains and left/right node contributions per node for each feature.

It is possible that not all nodes can be split on each feature. Hence, the list of possible nodes can differ between the features. Therefore, we return node_ids_list for each feature, containing the list of nodes that this feature can be used to split.

In this manner, the output is the best split per features and per node, so that it needs to be combined later to produce the best split for each node (among all possible features).

The output shapes are compatible in a way that the first dimension of all tensors are the same and equal to the number of possible split nodes for each feature.

node_id_range A Tensor of type int32. A Rank 1 tensor (shape=[2]) to specify the range [first, last) of node ids to process within stats_summary_list. The nodes are iterated between the two nodes specified by the tensor, as like for node_id in range(node_id_range[0], node_id_range[1]) (Note that the last index node_id_range[1] is exclusive).
stats_summary_indices A Tensor of type int32. A Rank 2 int64 tensor of dense shape N, 4 for accumulated stats summary (gradient/hessian) per node per bucket for each feature. The second dimension contains node id, feature dimension, bucket id, and stats dim. stats dim is the sum of logits dimension and hessian dimension, hessian dimension can either be logits dimen