docs: function(sql, callback){
      pg.connect(this.conn, function(err, client, done) {
        if(err) {
          return console.error('!error fetching client from pool', err);
        }
        client.query(sql, function(err, result) {
          //call `done()` to release the client back to the pool
          done();
          if ( callback ) {
            callback(err, result);
          }
        });
      });
  
    }