The PMTCalib package is intended to do PMT calibration.
For further information please refer to the paper describing it: L. N. Kalousis, J. P. A. M. de André, E. Baussan and M. Dracos, "A fast numerical method for photomultiplier tube calibration," JINST 15 (2020) no.03, [arXiv:1911.06220].