docs: def to_funset(self):
          """
          Converts the list of logical networks to a set of `gringo.Fun`_ instances
  
          Returns
          -------
          set
              Representation of all networks as a set of `gringo.Fun`_ instances
  
  
          .. _gringo.Fun: http://potassco.sourceforge.net/gringo.html#Fun
          """
          fs = set((gringo.Fun("variable", [var]) for var in self.hg.nodes))
  
          formulas = set()
          for network in self:
              formulas = formulas.union(it.imap(lambda (_, f): f, network.formulas_iter()))
  
          formulas = pd.Series(list(formulas))
  
          for i, network in enumerate(self):
              for v, f in network.formulas_iter():
                  fs.add(gringo.Fun("formula", [i, v, formulas[formulas == f].index[0]]))
  
          for formula_idx, formula in formulas.iteritems():
              for clause in formula:
                  clause_idx = self.hg.clauses_idx[clause]
                  fs.add(gringo.Fun("dnf", [formula_idx, clause_idx]))
                  for variable, sign in clause:
                      fs.add(gringo.Fun("clause", [clause_idx, variable, sign]))
  
          return fs