def event_filters(&blk)
      if block_given?
        self.event_filters.select(&blk)
      else
        Thresholds.new(@thresholds.select{|t| t.class.to_s == "Threshold::EventFilter"})
      end
    end
def event_filters(&blk)
      if block_given?
        self.event_filters.select(&blk)
      else
        Thresholds.new(@thresholds.select{|t| t.class.to_s == "Threshold::EventFilter"})
      end
    end
Returns a new Threshold Object with just event_filters