H5P_SET_BTREE_RATIOS sets the B-tree split ratios for a dataset transfer property list. The split ratios determine what percent of children go in the first node when a node splits.
left is used when the splitting node is the left-most node at its level in the tree; the ratio
right is used when the splitting node is the right-most node at its level; and the ratio
middle is used for all other cases.
A node which is the only node at its level in the tree uses the ratio
right when it splits.
All ratios are real numbers between 0 and 1, inclusive.