H5R_OPEN_REGION creates a copy of the dataspace of the dataset pointed to by a region reference,
ref_ptr, and defines a selection matching the selection pointed to by
ref_ptr within the dataspace copy.
rapl id is a reference access property list identifier for the reference. The access property list can be used to access external files that the reference points to (through a file access property list).
oapl id is an object access property list identifier for the referenced object. The access property list must be of the same type as the object being referenced, that is a dataset property list in that case.
Use H5S_CLOSE to release the dataspace identifier returned by this function when the identifier is no longer needed.