code: def trim_shared_suffix(ref, alt):
      
      n_ref = len(ref)
      n_alt = len(alt)
      n_min = min(n_ref, n_alt)
      i = 0
      while i < n_min and ref[-i - 1] == alt[-i - 1]:
          i += 1
  
      # i is length of shared suffix.
      if i == 0:
          return (ref, alt, '')
      return (ref[:-i], alt[:-i], ref[-i:])
docs: Reuse the `trim_shared_prefix` function above to implement similar
      functionality for string suffixes.
  
      Given ref='ABC' and alt='BC', we first revese both strings:
          reverse_ref = 'CBA'
          reverse_alt = 'CB'
      and then the result of calling trim_shared_prefix will be:
          ('A', '', 'CB')
      We then reverse all three of the result strings to get back
      the shared suffix and both prefixes leading up to it:
          ('A', '', 'BC')