def abslines(x,a,b,c,d):
    return np.piecewise(x, [x < -b/a, x >= -b/a], [lambda x: a*x+b+d, lambda x: c*(x+b/a)+d])

p0=[-0.001,0.2,0.005,0.]

bounds=([-1.,0.,0.,0.],[0.,1.,1.,1.])
bounds=([-0.5,0.01,0.0001,0.],[-0.001,0.5,0.5,1.])
bounds=([-0.1,0.01,0.0001,0.],[-0.001,0.5,0.1,1.])
bounds=([-0.01,0.1,0.0001,0.],[-0.001,0.5,0.1,1.])