text: import lenstronomy.Util.util as util
  
  
  instrument_name_list = ['LSST']
  observation_name_list = ['LSST_g_band', 'LSST_r_band', 'LSST_i_band']
  
  
  def observation_constructor(instrument_name, observation_name):
      """
  
      :param instrument_name: string, name of instrument referenced in this file
      :param observation_name: string, name of observation referenced in this file
      :return: instance of the SimulationAPI.data_type instance
      """
  
      if instrument_name == 'LSST':
          kwargs_instrument = LSST_camera
      else:
          raise ValueError("instrument name %s not supported! Choose among  %s " % (instrument_name, instrument_name_list))
  
      if observation_name == 'LSST_g_band':
          kwargs_observation = LSST_g_band_obs
      elif observation_name == 'LSST_r_band':
          kwargs_observation = LSST_r_band_obs
      elif observation_name == 'LSST_i_band':
          kwargs_observation = LSST_i_band_obs
      else:
          raise ValueError('observation name %s not supported! Choose among %s' %
                           (observation_name, observation_name_list))
      kwargs_data = util.merge_dicts(kwargs_instrument, kwargs_observation)
      return kwargs_data
  
  
  LSST_camera = {'read_noise': 10,
                 'pixel_scale': 0.263,
                 'ccd_gain': 4.5}
  
  LSST_g_band_obs = {'exposure_time': 90.,
                     'sky_brightness': 21.7,
                     'magnitude_zero_point': 30,
                     'num_exposures': 10,
                     'seeing': 0.9,
                     'psf_type': 'GAUSSIAN'}
  
  LSST_r_band_obs = {'exposure_time': 90.,
                     'sky_brightness': 20.7,
                     'magnitude_zero_point': 30,
                     'num_exposures': 10,
                     'seeing': 0.9,
                     'psf_type': 'GAUSSIAN'}
  
  LSST_i_band_obs = {'exposure_time': 90.,
                     'sky_brightness': 20.1,
                     'magnitude_zero_point': 30,
                     'num_exposures': 10,
                     'seeing': 0.9,
                     'psf_type': 'GAUSSIAN'}
  