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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 prox_gradf12(x, step, j=None, Xs=None):
 """1D gradient operator for x or y"""

    if j == 0:
        return x - step*grad_fx(Xs[0][0], Xs[1][0])
    if j == 1:
        y = x
        return y - step*grad_fy(Xs[0][0], Xs[1][0])
    raise NotImplementedError