How to calculate the product ion mz provided with ion type?

[manto...@gmail.com]

Hi~

If I have a peptide 'AAAM(UniMod:34)EK' in OpenMS format, how to calculate the b5_2 product ion mz?

Currently, I have to get the product ion seq 'AAAM(UniMod:34)E' and call the pyteomics.mass.calculate_mass function. Is there an convenient way to replace the fallible method?

Thanks.