code: def search_disk_size(self, search_index):
          
          ddoc_search_disk_size = self.r_session.get(
              '/'.join([self.document_url, '_search_disk_size', search_index]))
          ddoc_search_disk_size.raise_for_status()
          return response_to_json_dict(ddoc_search_disk_size)
docs: Retrieves disk size information about a specified search index within
          the design document, returns dictionary
  
          GET databasename/_design/{ddoc}/_search_disk_size/{search_index}