input: Write a function to get the list of zones from the Cloudflare API.
  assert isinstance(CloudflareApi('your_username', 'your_api_key').get_zone_list(), dict)
  assert 'result' in CloudflareApi('your_username', 'your_api_key').get_zone_list()
output: import requests
  
  class CloudflareApi:
      def __init__(self, username, api_key):
          self.username = username
          self.api_key = api_key
          self.base_url = "https://api.cloudflare.com/client/v4"
  
      def get_zone_list(self):
          url = f"{self.base_url}/zones"
          headers = {
              "X-Auth-Email": self.username,
              "X-Auth-Key": self.api_key,
              "Content-Type": "application/json"
          }
          response = requests.get(url, headers=headers)
          return response.json()