code: def get_area_def(self, dsid):
          
          msg = self._get_message(self._msg_datasets[dsid])
          try:
              return self._area_def_from_msg(msg)
          except (RuntimeError, KeyError):
              raise RuntimeError("Unknown GRIB projection information")
docs: Get area definition for message.
  
          If latlong grid then convert to valid eqc grid.