H5VLattr_optional_op

herr_t H5VLattr_optional_op(void *  attr,  hid_t connector_id,  int  opt_type,
       hid_t dxpl_id,  void * *  req, ...)

Performs an optional operation on an attribute using op type.

`attr`	Attribute object
`connector_id`	VOL connector identifier
`opt_type`	Optional operation type
`dxpl_id`	Data transfer property list
`req`	Async request object (can be null)
`arguments`	Variable arguments for the operation

Non-negative on success, negative on failure.