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
Compute covariance of two numeric array

    Parameters
    ----------
    how : {'sample', 'pop'}, default 'sample'

    Returns
    -------
    cov : double scalar