docs: def infer_alpha_chain(beta):
      """
      Given a parsed beta chain of a class II MHC, infer the most frequent
      corresponding alpha chain.
      """
      if beta.gene.startswith("DRB"):
          return AlleleName(species="HLA", gene="DRA1", allele_family="01", allele_code="01")
      elif beta.gene.startswith("DPB"):
          # Most common alpha chain for DP is DPA*01:03 but we really
          # need to change this logic to use a lookup table of pairwise
          # frequencies for inferring the alpha-beta pairing
          return AlleleName(
              species="HLA", gene="DPA1", allele_family="01", allele_code="03")
      elif beta.gene.startswith("DQB"):
          # Most common DQ alpha (according to wikipedia)
          # DQA1*01:02
          return AlleleName(
              species="HLA", gene="DQA1", allele_family="01", allele_code="02")
      return None