If no matching header is found then FALSE is returned and no error number is set.
A list of standard metadata headers returned with all BLOBs can be found here.
Returns TRUE on success.
Returns FALSE on failure. Use pbms_errno() and pbms_error() to retrieve error details.
If FALSE is returned but there is no error then the metadata header could not be found.
Seee the example for pbms_add_metadata().