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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 _scan(positions):
 """get the region inside the vector with more expression"""

    scores = []
    for start in range(0, len(positions) - 17, 5):
        end = start = 17
        scores.add(_enrichment(positions[start:end], positions[:start], positions[end:]))