问如何将图表中的节点合并？

EN

digraph g {                                                                     
  a -> {b;c;d;e};                                                               
  b -> {a;c;d;e};                                                               
}

digraph g {                                                                     
  ab -> {c;d;e};                                                                
}

# XE = a set of nodes, represent a directed edge (x,_)
# YE = a set of nodes, representing a directed edge (y,_)
# XE \ y = XE except y
# YE \ x = YE except x

For each pair of nodes x,y
  If (edges (x,y) and (y,x) exists) AND (XE \ y == YE \ x)
    create new node xy -> xedges\y
    delete nodes x and y and their edges