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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:
 """trim a sequence to include the left and right flanking sequences of size `flank`, with the intervening sequence elided by `elision`. 'ABCDE..VWXYZ' 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' 'ABCDEFGHIJKL.OPQRSTUVWXYZ' """


    elided_sequence_len = flank + flank + len(elision)
    if len(s) <= elided_sequence_len:
        return s
    return s[:flank] + elision + s[-flank:]