code: def get_aoi(self, solar_zenith, solar_azimuth):
          
  
          aoi = irradiance.aoi(self.surface_tilt, self.surface_azimuth,
                               solar_zenith, solar_azimuth)
          return aoi
docs: Get the angle of incidence on the system.
  
          Parameters
          ----------
          solar_zenith : float or Series.
              Solar zenith angle.
          solar_azimuth : float or Series.
              Solar azimuth angle.
  
          Returns
          -------
          aoi : Series
              The angle of incidence