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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def cdna_codon_sequence_after_deletion_or_substitution_frameshift( sequence_from_start_codon, cds_offset, trimmed_cdna_ref, trimmed_cdna_alt):
 """ Logic for any frameshift which isn't an insertion. We have insertions as a special case since our base-inclusive indexing means something different for insertions: cds_offset = base before insertion Whereas in this case: cds_offset = first reference base affected by a variant Returns index of first modified codon and sequence from that codon onward. """

    mutated_codon_index = cds_offset // 3
    # get the sequence starting from the first modified codon until the end
    # of the transcript.
    sequence_after_mutated_codon = \
        sequence_from_start_codon[mutated_codon_index * 3:]

    # the variant's ref nucleotides should start either 0, 1, or 2 nucleotides
    # into `sequence_after_mutated_codon`
    offset_into_mutated_codon = cds_offset % 3

    sequence_from_mutated_codon = substitute(
        sequence=sequence_after_mutated_codon,
        offset=offset_into_mutated_codon,
        ref=trimmed_cdna_ref,
        alt=trimmed_cdna_alt)
    return mutated_codon_index, sequence_from_mutated_codon