code: def get_data_model(self):
          
          if len(DM):
              self.dm = DM
              self.crit_map = CRIT_MAP
              return
          if not set_env.OFFLINE:
              dm = self.get_dm_online()
              if dm:
                  print('-I- Using online data model')
                  #self.cache_data_model(dm)
                  return self.parse_response(dm)
          # if online is not available, get cached dm
          dm = self.get_dm_offline()
          print('-I- Using cached data model')
          return self.parse_cache(dm)
docs: Try to download the data model from Earthref.
          If that fails, grab the cached data model.