Dikshant jha issues

Results 3 issues of


                                            Dikshant jha

i have changed some of the funtions docstring ,if they are okay then we can update that throughout our code base.

these are some of the changes to reduce errors occuring while testing + i have added the doctest for quicktest.md (rest are still pending ).

correct the USI values in the spectrum_utils docs and check all the mentioned example .

good first issue

documentation