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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 angstrom_alpha(aod1, lambda1, aod2, lambda2):
 r""" Calculate Angstrom alpha exponent. Parameters aod1 : numeric first aerosol optical depth lambda1 : numeric wavelength in nanometers corresponding to ``aod1`` aod2 : numeric second aerosol optical depth lambda2 : numeric wavelength in nanometers corresponding to ``aod2`` Returns ------- alpha : numeric Angstrom :math:`\alpha` exponent for AOD in ``(lambda1, lambda2)`` See also -------- angstrom_aod_at_lambda """

    return - np.log(aod1 / aod2) / np.log(lambda1 / lambda2)