digraph {
  bgcolor = transparent
  rankdir = LR
  splines = line
  ranksep = 1

  subgraph cluster_l1 {
    style = dotted
    l1d2 [label = "⋮" shape = none]
    l1n3 [shape = circle width = 0.75 label = ""]
    l1n2 [shape = circle width = 0.75 label = <<i>k</i>-th>]
    l1n1 [shape = circle width = 0.75 label = ""]
    l1d1 [label = "⋮" shape = none]
    l1 [label = <layer <i>i</i>&minus;1<br/>neurons> shape = none]
  }

  subgraph cluster_l2 {
    style = dotted
    l2d2 [label = "⋮" shape = none]
    l2n3 [shape = circle width = 0.75 label = ""]
    l2n2 [shape = circle width = 0.75 label = <<i>j</i>-th>]
    l2n1 [shape = circle width = 0.75 label = ""]
    l2d1 [label = "⋮" shape = none]
    l2 [label = <layer <i>i</i><br/>neurons> shape = none]
  }

    subgraph cluster_l3 {
    style = dotted
    l3d2 [label = "⋮" shape = none]
    l3n3 [shape = circle width = 0.75 label = ""]
    l3n2 [shape = circle width = 0.75 label = ""]
    l3n1 [shape = circle width = 0.75 label = ""]
    l3d1 [label = "⋮" shape = none]
    l3 [label = <layer <i>i</i>+1<br/>neurons> shape = none]
  }

  l1d1 -> l2d1 [style = invis]
  l2d1 -> l3d1 [style = invis]

  l1n1:e -> l2n1:w [dir = none style = invis]
  l1n2:e -> l2n2:w [dir = none]
  l1n3:e -> l2n3:w [dir = none style = invis]

  l2n1:e -> l3n1:w [dir = none style = invis]
  l2n2:e -> l3n2:w [dir = none style = invis]
  l2n3:e -> l3n3:w [dir = none style = invis]

  l1d2 -> l2d2 [style = invis]
  l2d2 -> l3d2 [style = invis]

  l1 -> l2 [constraint = false label = "forward"]
  l2 -> l3 [constraint = false label = "forward"]
}