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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 abcd2 (x0, y0, a, b, c, x, y):
 """Given an 2D Gaussian expressed as the ABC polynomial coefficients, compute a "squared distance parameter" such that z = exp (-0.5 * d2) Inputs: * x0: position of Gaussian center on x axis * y0: position of Gaussian center on y axis * a: such that z = exp (ax² + bxy + cy²) * b: see above * c: see above * x: x coordinates of the locations for which to evaluate d2 * y: y coordinates of the locations for which to evaluate d2 Returns: d2, distance parameter defined as above. This is pretty trivial. """

    _abccheck (a, b, c)
    dx, dy = x - x0, y - y0
    return -2 * (a * dx**2 + b * dx * dy + c * dy**2)