Error creating GIF using images2gif.py

Error creating GIF using images2gif.py

I'm trying to create a GIF file using images2fig.py from the visvis package
With this very simple code
import glob
from PIL import Image
from visvis.vvmovie.images2gif import writeGif
images = [Image.open(image) for image in glob.glob("*.png")]
filename = "test.gif"
writeGif(filename, images, duration=0.2)
I got an error
writeGif(filename, images, duration=0.2)
File "C:\Python27\lib\site-packages\visvis\vvmovie\images2gif.py", line
570, in writeGif
images = gifWriter.convertImagesToPIL(images, dither, nq)
File "C:\Python27\lib\site-packages\visvis\vvmovie\images2gif.py", line
373, in convertImagesToPIL
im = Image.fromarray(im,'RGB')
File "C:\Python27\lib\site-packages\PIL\Image.py", line 1937, in fromarray
obj = obj.tobytes()
AttributeError: 'numpy.ndarray' object has no attribute 'tobytes'
What did I do wrong? How do I fix this?