Example observed-frame SDSS quasar spectrum and data/continuum model ratio spectra after removing the features of quasar emission and converting to unit average flux density with the package PyQSOFIT (Guo et al. 2018). On top, we show the original SDSS spectrum, with the multi-component fit performed with PyQSOFIT in colour. The bottom panel displays the resulting quasar spectrum normalised to an arbitrary value of 1 by dividing the observed spectrum by the continuum.