generators.ET0LTreeGrammar:
  ( { S },
    { F:4, G:4, H:4, S:0, leaf:0 },
    {
      {
        S -> F[S,S,S,S],
        S -> G[S,S,S,S],
        S -> H[S,S,S,S]
      },
      {
        S -> leaf
      }
    },
    S )
