![graphiz nodes](https://camo.githubusercontent.com/50bbbe03a9ff3c3da22394c106942a1e6e54c82a400d26e13a713c04aa6649b7/68747470733a2f2f692e696d6775722e636f6d2f623446743644512e706e67)
puts Contact.all.map { |c| "C#{c.id} [style=filled,color=greenyellow]" } +
Book.all.map { |b| "B#{b.id} [style=filled,color=lightcyan]" } +
BookContact.all.map { |bc| "C#{bc.contact_id} -> B#{bc.book_id}" }
digraph G {
C1 [style=filled,color=greenyellow]
C2 [style=filled,color=greenyellow]
C3 [style=filled,color=greenyellow]
C4 [style=filled,color=greenyellow]
C5 [style=filled,color=greenyellow]
C6 [style=filled,color=greenyellow]
C7 [style=filled,color=greenyellow]
C8 [style=filled,color=greenyellow]
C9 [style=filled,color=greenyellow]
C10 [style=filled,color=greenyellow]
B1 [style=filled,color=lightcyan]
B2 [style=filled,color=lightcyan]
B3 [style=filled,color=lightcyan]
B4 [style=filled,color=lightcyan]
B5 [style=filled,color=lightcyan]
B6 [style=filled,color=lightcyan]
C1 -> B1
C2 -> B1
C1 -> B2
C2 -> B2
C3 -> B2
C4 -> B2
C4 -> B3
C5 -> B3
C6 -> B3
C3 -> B4
C4 -> B4
C5 -> B4
C6 -> B4
C1 -> B1
C10 -> B1
}