Scrapy: Getting 403 Client Error from API post request

Question

In body data, there are 3 null vale and I convert them into None and get ride of NameError: name 'null' is not defined but getting 403. How to solve the problem?

import scrapy
from scrapy.http import Request
import json

class OpenSeaSpider(scrapy.Spider):
    name = 'opensea'
    start_urls = ['https://opensea.io/rankings']

    def parse(self, response):
        api_url = 'https://api.opensea.io/graphql/'

        headers = {
            'Content-Type':'application/json',
            'x-api-key':'2f6f419a083c46de9d83ce3dbe7db601',
            'x-build-id': 'MlecpAI7Iur8bjb55hxna',
            'x-signed-query': '89e599cadfd5ff7451e909df00286466a8fb1fec24566e7d22b0bf376779b7ca'

            }

        data = {"id":"RankingsPagePaginationQuery","query":"query RankingsPagePaginationQuery(\n  $chain: [ChainScalar!]\n  $count: Int\n  $createdAfter: DateTime\n  $cursor: String\n  $parents: [CollectionSlug!]\n  $sortBy: CollectionSort\n) {\n  ...RankingsPage_data\n}\n\nfragment RankingsPage_data on Query {\n  rankings(after: $cursor, chains: $chain, first: $count, sortBy: $sortBy, parents: $parents, createdAfter: $createdAfter) {\n    edges {\n      node {\n        createdDate\n        name\n        slug\n        logo\n        isVerified\n        floorPrice\n        stats {\n          marketCap\n          numOwners\n          totalSupply\n          sevenDayChange\n          sevenDayVolume\n          oneDayChange\n          oneDayVolume\n          thirtyDayChange\n          thirtyDayVolume\n          totalVolume\n          id\n        }\n        id\n        __typename\n      }\n      cursor\n    }\n    pageInfo {\n      endCursor\n      hasNextPage\n    }\n  }\n}\n","variables":{"chain":null,"count":100,"createdAfter":null,"cursor":"YXJyYXljb25uZWN0aW9uOjk5","parents":null,"sortBy":"SEVEN_DAY_VOLUME"}}

        return Request(
            url=api_url,
            method='POST',
            headers=headers,
            body=json.dumps(data),
            callback=self.start
        )

    def start(self, response):
        resp= json.loads(response.body)
        print(resp)