Filtering types available in Obspy.

Good afternoon, I just reviewed the filtering tutorial. Here in Peru this topic of accelerogram analysis is not very widespread and most people limit themselves to using the Seismosignal program, in which they are often not very sure about what input parameters to use. I am currently working on my undergraduate thesis and need to learn more about filtering. I have two queries and I hope you can help me. a) I have been reviewing the filtering that was carried out for the earthquake that occurred in Lima during 1966 (attached image). In the image you can see that a bandpass filter is made between 0.05-0.07 and 25.00-27.00. What type of filtering is this, in which cases should it be carried out and how do we apply it in Obspy?
b) I would like you to be able to help me by providing a bibliography or some standard guide to carry out an adequate filtering process.
I sincerely hope that you can help me because this is very important to me. Thanks in advance.

I do not understand that part, it would be quite unusual to apply a bandpass with two separate frequency ranges (or I am missing something here)

Basic info on filtering can be found here:

Bandpass works similar, you just need kwargs freqmin and freqmax instead of freq to specify the passband.

Maybe you can find something helpful in the New Manual of Observatory Practice, it’s a free resource:
Chapter 11 has some parts on filtering: