code: def compute_offset_to_first_complete_codon(
          offset_to_first_complete_reference_codon,
          n_trimmed_from_reference_sequence):
      
      if n_trimmed_from_reference_sequence <= offset_to_first_complete_reference_codon:
          return (
              offset_to_first_complete_reference_codon -
              n_trimmed_from_reference_sequence)
      else:
          n_nucleotides_trimmed_after_first_codon = (
              n_trimmed_from_reference_sequence -
              offset_to_first_complete_reference_codon)
          frame = n_nucleotides_trimmed_after_first_codon % 3
          return (3 - frame) % 3
docs: Once we've aligned the variant sequence to the ReferenceContext, we need
      to transfer reading frame from the reference transcripts to the variant
      sequences.
  
      Parameters
      ----------
      offset_to_first_complete_reference_codon : int
  
      n_trimmed_from_reference_sequence : int
  
      Returns an offset into the variant sequence that starts from a complete
      codon.