fix colormap and pandas issues with pkg version updates

[jianheACM]

With matplotlib version 3.6+, matplotlib.cm.get_cmap is deprecated. There are some incompatibility with pandas with the latest version. I have made the fixes and they are now working properly.
However, we need to pay attention on this for the future updates. I'm worried we may have the similar issues in the future.

[zmoon]

some incompatibility with pandas with the latest version

To be clear, this was a bug in one pandas release, which has since been fixed, as we discussed in #135. If you install the latest pandas, there wouldn't be an issue.

we need to pay attention on this for the future updates

Yep, this is part of package maintenance.

[jianheACM]

@zmoon @rschwant I have updated the code as suggested. Could you please take a look?

[zmoon]

@jianheACM 4b9f5b4 is what I meant by my comment. Would you be able to try it out?

[rschwant]

For some reason, when I test using the develop_reg2 branch directly (Maybe this doesn't have the code completely set up?), for the bias plot I get the viridis colorbar instead of OrangeBlue? But I just realized, Zach you updated something, so let me retry it.

[rschwant]

Thanks Zach and Jian for working on this! With your recent update now Zach, it works well and I'm no longer getting viridis as the colorbar, so I approve. @jianheACM as long as you are okay with Zach's changes, this can be merged.

[jianheACM]

@zmoon @rschwant I also tested on my side and it is working perfectly. Thanks!