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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 covariance(left, right, where=None, how='sample'):
 """ Compute covariance of two numeric array Parameters how : {'sample', 'pop'}, default 'sample' Returns ------- cov : double scalar """

    expr = ops.Covariance(left, right, how, where).to_expr()
    return expr