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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 PorodGuinier(q, a, alpha, Rg):
 """Empirical Porod-Guinier scattering Inputs: ------- ``q``: independent variable ``a``: factor of the power-law branch ``alpha``: power-law exponent ``Rg``: radius of gyration Formula: -------- ``G * exp(-q^2*Rg^2/3)`` if ``q>q_sep`` and ``a*q^alpha`` otherwise. ``q_sep`` and ``G`` are determined from conditions of smoothness at the cross-over. Literature: B. Hammouda: A new Guinier-Porod model. J. Appl. Crystallogr. (2010) 43, 716-719. """

    return PorodGuinierMulti(q, a, alpha, Rg)