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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 mark_point(img, x, y):
 """ Mark a point Args: - img(numpy):
 the source image - x, y(int):
 position """

    overlay = img.copy()
    output = img.copy()

    alpha = 0.5
    radius = max(5, min(img.shape[:2])//15)
    center = int(x), int(y)
    color = (0, 0, 255)

    cv2.circle(overlay, center, radius, color, -1)
    cv2.addWeighted(overlay, alpha, output, 1-alpha, 0, output)
    return output