code: def ssp(V,E):
      
      model = Model("ssp")
  
      x = {}
      for i in V:
          x[i] = model.addVar(vtype="B", name="x(%s)"%i)
  
      for (i,j) in E:
          model.addCons(x[i] + x[j] <= 1, "Edge(%s,%s)"%(i,j))
  
      model.setObjective(quicksum(x[i] for i in V), "maximize")
  
      model.data = x
      return model
docs: ssp -- model for the stable set problem
      Parameters:
          - V: set/list of nodes in the graph
          - E: set/list of edges in the graph
      Returns a model, ready to be solved.