如何在matplotlib中将colormap的子集提取为新的colormap？

I would like to use a colormap from matplotlib e.g. CMRmap. But I don't want to use the "black" color at the beginning and the "white" color at the end. I'm interested to plot my data using the in-between colors. I think ppl use it quite often but I was searching over internet and could not manage to find any simple solution. I'll appreciate if someone suggest any solution.I would like to use a colormap from matplotlib