docs: def get_split_pos_lines(data, cgi_input, header):
      """Advance across split alleles and return data from each.
  
      CGI var file reports alleles separately for heterozygous sites:
      all variant or reference information is called for the first allele,
      then for the second. This function moves forward in the file to
      get lines for each (and ends up with one remaineder line as well).
      """
      s1_data = [data]
      s2_data = []
      next_data = cgi_input.readline().decode('utf-8').rstrip('\n').split("\t")
      while next_data[header['allele']] == "1":
          s1_data.append(next_data)
          next_data = cgi_input.readline().decode('utf-8').rstrip('\n').split("\t")
      while next_data[header['allele']] == "2":
          s2_data.append(next_data)
          next_data = cgi_input.readline().decode('utf-8').rstrip('\n').split("\t")
      return s1_data, s2_data, next_data