generators.ET0LTreeGrammar("coloured hexagonal knots"):
( { A, B, T, N },
  { F:6, G: 4, H:3, I:2, tile1:0, tile2:0, tile3:0, outer:0, background:0, +:2, gr:1, rot:1,
    A:0, B:0, T:0, N:0 },
  {
    {
      A -> G[N, rot[gr[N]], gr[A], gr[B]],
      B -> H[T, rot[gr[N]], gr[B]],
      T -> tile1,
      N -> tile1
    },
    {
      A -> G[N, rot[gr[N]], gr[A], gr[B]],
      B -> H[T, rot[gr[N]], gr[B]],
      T -> tile2,
      N -> tile2
    },
    {
      A -> G[N, gr[N], gr[A], gr[B]],
      B -> H[T, gr[N], gr[B]],
      T -> tile3,
      N -> tile1
    },
    {
      A -> G[tile1, gr[outer], background, background],
      B -> H[tile1, gr[outer], background],
      T -> tile1,
      N -> tile1
    },
    {
      A -> G[tile2, gr[outer], background, background],
      B -> H[tile2, gr[outer], background],
      T -> tile2,
      N -> tile2
    },
    {
      A -> G[tile1, gr[outer], background, background],
      B -> H[tile3, gr[outer], background],
      T -> tile3,
      N -> tile1
    }
  },
  F[A, A, A, A, A, A],
  (1,2,3)* (4,5,6)
)
