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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 _get_flag(which, flags):
 """ Find 'which' entry in 'flags'. """

    res = [this for this in flags if this.is_equal(which)]
    if len(res) == 0:
        return None
    if len(res) == 1:
        return res[0]
    assert()