From which league is the player chosen by the Atlanta Thrashers (from Dallas) 6?
CREATE TABLE "round_four" (
  "pick_num" real,
  "player" text,
  "nationality" text,
  "position" text,
  "nhl_team" text,
  "team_from" text,
  "league_from" text
);
SELECT "league_from" FROM "round_four" WHERE "nhl_team"='atlanta thrashers (from dallas) 6';