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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 _truncate(self, x, k):
        ''' given a vector x, leave its top-k absolute-value entries alone, and set the rest to 0 '''
        not_F = np.argsort(np.abs(x))[:-k]
        x[not_F] = 0
        return x