def mutate_keyframes_into_deltaframes! range = nil
      range = 0..self.size if range.nil?
      self.each_with_index do |frame, i|
        if range.include? i
          frame.flag = 0 if frame.is_keyframe?
        end
      end
      self
    end
def mutate_keyframes_into_deltaframes! range = nil
      range = 0..self.size if range.nil?
      self.each_with_index do |frame, i|
        if range.include? i
          frame.flag = 0 if frame.is_keyframe?
        end
      end
      self
    end
Mutates keyframes into deltaframes at given range, or all.