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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 nearest_intersection_idx(a, b):
 """Determine the index of the point just before two lines with common x values. Parameters a : array-like 1-dimensional array of y-values for line 1 b : array-like 1-dimensional array of y-values for line 2 Returns ------- An array of indexes representing the index of the values just before the intersection(s) of the two lines. """

    # Difference in the two y-value sets
    difference = a - b

    # Determine the point just before the intersection of the lines
    # Will return multiple points for multiple intersections
    sign_change_idx, = np.nonzero(np.diff(np.sign(difference)))

    return sign_change_idx