Corrected azimuth, taking into account backsight, declination, and compass corrections.

def azm(self):
        """Corrected azimuth, taking into account backsight, declination, and compass corrections."""
        azm1 = self.get('BEARING', None)
        azm2 = self.get('AZM2', None)
        if azm1 is None and azm2 is None:
            return None
        if azm2 is None:
            return azm1 + self.declination
        if azm1 is None:
            return (azm2 + 180) % 360 + self.declination
        return (azm1 + (azm2 + 180) % 360) / 2.0 + self.declination