text: Title: How to add color legend for predicted masks in semantic segmentation? 
  Body: Thank you very much for this great work. The tools and tutorials are really great to follow, and they encourage people from a non-technical background like me to enjoy CV and get a taste of deep learning.
  
  May I have a question about plotting predicted masks in the semantic segmentation, please. I was following [this official tutorial](https://gluon-cv.mxnet.io/build/examples_segmentation/demo_psp.html). After predicting using a pre-trained model, I want to plot the masks together with a legend bar to indicate which color represents what class. Like a blue square with the text "water". Is there an easy way to add the legend bar and associated texts? I found a [repo](https://github.com/RomRoc/deeplab_retrain_ade20k_colab) that may provide a solution by hard coding a lot, but it looks difficult for me so far.
  
  Since there is a handy function `get_color_pallete(predict, 'ade20k')` to help transform the mask color to 'ade20k', is it possible to enhance one of the utility functions to add a color legend with text?
  