<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def search_disk_size(self, search_index):
 """ Retrieves disk size information about a specified search index within the design document, returns dictionary GET databasename/_design/{ddoc}/_search_disk_size/{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)