def round_robin?(flight_id=0)
      #each round-robin round should contains n-1 games where n is the nbr of teams (:dummy included if odd)
      return false if self.rounds[flight_id].size != (@flights[flight_id].size*self.cycles)-self.cycles

      #check if each team plays the same number of games against each other
      @flights[flight_id].each do |t1|
        @flights[flight_id].reject{|t| t == t1}.each do |t2|
          return false unless face_to_face(t1,t2).size == self.cycles || [t1,t2].include?(:dummy)
        end
      end
      return true
    end
def round_robin?(flight_id=0)
      #each round-robin round should contains n-1 games where n is the nbr of teams (:dummy included if odd)
      return false if self.rounds[flight_id].size != (@flights[flight_id].size*self.cycles)-self.cycles

      #check if each team plays the same number of games against each other
      @flights[flight_id].each do |t1|
        @flights[flight_id].reject{|t| t == t1}.each do |t2|
          return false unless face_to_face(t1,t2).size == self.cycles || [t1,t2].include?(:dummy)
        end
      end
      return true
    end
returns true if the generated schedule is a valid round-robin (for testing purpose)