cl.flipper( scale=None ) seems not working

[cylGitHub18]

Dear developers of colorlover tool,
I was trying to reverse the colors of "Spectral" in the Diverging category. I thought the function cl.flipper( scale=None ) could achieve this. However, it didn't. From your GitHub webpage, the results of cl.flipper()['div']['3']['RdYlBu'] and cl.scales['3']['div']['RdYlBu'] are the same, the same sequence of the three returned rgb combinations. This perhaps explains why I didn't see reverse Spectral. I tried cl.scales['3']['div']['Spectral_r'], i.e., by adding _r, and it didn't work either. I am not sure if this is a problem or not. Could you please teach me how to reverse the color scale of your tool? Thank you in advance for your insights.