Struct defining a set and its attributes and types
t() :: %Mtg.Set{ block: binary(), booster: [binary() | [binary()]], border: binary(), code: binary(), gatherer_code: binary(), magic_cards_info_code: binary(), mkm_id: integer(), mkm_name: binary(), name: binary(), old_code: binary(), online_only: boolean(), release_date: binary(), type: binary() }