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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 _common(s1, s2, i1, i2):
 """calculate the common % percentage of sequences"""

    c = len(set(s1).intersection(s2))
    t = min(len(s1), len(s2))
    pct = 1.0 * c / t * t
    is_gt = up_threshold(pct, t * 1.0, parameters.similar)
    logger.debug("_common: pct %s of clusters:%s %s = %s" % (1.0 * c / t, i1, i2, is_gt))
    if pct < parameters.similar and is_gt and pct > 0:
        pct = parameters.similar
    return pct / t