Provide some logging option for GraphQlQuery

Currently there is no easy option to print out how the GraphQL query in GraphQlQuery object looks like.

Use case:
I am building GraphQlQuery and would like to print the query out and check it visually or use int in GraphQl explorer on the server.

I used query.calculate_query() but it wasn't too obvious.

从 GraphQlQuery 对象及其 calculate_query() 方法开始，issue 将其确定为当前获取 query 的方式。检查计算出的 query 是如何表示的，以及可以在哪里加入 logging 或检查选项。当用户可以轻松打印或复制生成的 GraphQL query，以便进行可视化检查或在 GraphQL Explorer 中使用时，即视为完成。