checks if provided string is a valid Guid a valid GUID has the form XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXX when X is a hexadecimal digit
the GUID to test for validaty
checks if provided string is a valid Guid a valid GUID has the form XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXX when X is a hexadecimal digit