code: def _build_obs(self, **kwargs):
          
          logging.debug('Building ObservationTree...')
          tree = ObservationTree()
          for k,v in kwargs.items():
              if k in self.ic.bands:
                  if np.size(v) != 2:
                      logging.warning('{}={} ignored.'.format(k,v))
                      # continue
                      v = [v, np.nan]
                  o = Observation('', k, 99) #bogus resolution=99
                  s = Source(v[0], v[1])
                  o.add_source(s)
                  logging.debug('Adding {} ({})'.format(s,o))
                  tree.add_observation(o)
  
          self.obs = tree
docs: Builds ObservationTree out of keyword arguments
  
          Ignores anything that is not a photometric bandpass.
          This should not be used if there are multiple stars observed.
  
          Creates self.obs