docs: def pg_stat_statement(self):
          """
          Some queries require the pg_stat_statement module to be installed.
          http://www.postgresql.org/docs/current/static/pgstatstatements.html
  
          :returns: boolean
          """
  
          if self._pg_stat_statement is None:
              results = self.execute(sql.PG_STAT_STATEMENT)
              is_available = results[0].available
  
              if is_available:
                  self._pg_stat_statement = True
              else:
                  self._pg_stat_statement = False
  
          return self._pg_stat_statement