docs: def _is_postgres(self):
          """ Determine if the running engine is postgres """
          if self._is_postgres_engine is None:
              is_postgres_engine = False
              try:
                  dialect = self.session.bind.engine.name
                  if 'redshift' in dialect or 'postg' in dialect or 'pg' in \
                          dialect:
                      is_postgres_engine = True
              except:
                  pass
              self._is_postgres_engine = is_postgres_engine
          return self._is_postgres_engine