π-HelixNovo also employs a transformer architecture similar to Casanovo's. However, π-HelixNovo introduces the notion of a "complementary spectrum," in which, following a denoising step, each peak in the observed spectrum is reflected relative to the observed precursor m/z value. Thus, a b-ion in the observed spectrum is transformed into its corresponding y-ion in the complementary spectrum. In principle, this complementary spectrum can reconstruct some b-and y-ions when some b/y pairs are incomplete. This complementary spectrum is input to the encoder alongside the observed spectrum. Additionally, π-HelixNovo provides the precursor m/z value as an input to the encoder, rather than only providing it at the decoding step as in Casanovo.