If the constructor can take an option :formats => [ <array of RDF::Format classes> ]...
You gain control over what formats you allow
You gain control over which implementation is used in the case where more than one implementation for a mime type exists (eg, "pure" JSON versus rdf-raptor JSON)
You can specify a format preference order for resolving wildcards
If the constructor can take an option :formats => [ <array of RDF::Format classes> ]...