title: PIL is showing all the previous frames in the gif
body: <pre><code>pillow version:5.4.1
  </code></pre>
  
  <p>The problem is I can see all the frames in the gif.</p>
  
  <p><strong>Expectation</strong>: in the lifecycle of a gif having 5 frames each frames should be visible for a fraction of time and at the end of gif only 5th frame should be visible.</p>
  
  <p><strong>Actual</strong>: In my case at the end of the gif I can see all the frames 1-2-3-4-5.</p>
  
  <p>There are 5 frames in the gif animation and all the frames are in gif format(static) I also tried with png files too but I am getting the same result.</p>
  
  <p>All my frames are with transparent background.</p>
  
  <pre><code>from PIL import Image
  
  frame_list = []
  frame_list.append("object_1.gif")
  frame_list.append("object_2.gif")
  frame_list.append("object_3.gif")
  frame_list.append("object_4.gif")
  frame_list.append("object_5.gif")
  
  images = []
  for n in frame_list:
      frame = Image.open(n)
      images.append(frame)
  
  images[0].save('anitest.gif',
                 save_all=True,
                 format='GIF',
                 append_images=images[1:],
                 duration=200,
                 loop=0)
  </code></pre>
  
  <p>If anyone encountered the same issue please let me know what am I doing wrong?</p>
  
  <p><a href="https://i.stack.imgur.com/8zQPG.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8zQPG.gif" alt="enter image description here"></a></p>
  
  <p><strong>With the below code using imageio it's working but I am loosing transparency and its very slow compare PIL</strong> </p>
  
  <pre><code>images = []
  for filename in names:
      images.append(imageio.imread(filename))
  imageio.mimsave('anitest.gif', images,duration=0.3)
  </code></pre>