code: def GET_namespace_num_names(self, path_info, namespace_id):
          
          if not check_namespace(namespace_id):
              return self._reply_json({'error': 'Invalid namespace'}, status_code=400)
  
          blockstackd_url = get_blockstackd_url()
          name_count = blockstackd_client.get_num_names_in_namespace(namespace_id, hostport=blockstackd_url)
          if json_is_error(name_count):
              log.error("Failed to load namespace count for {}: {}".format(namespace_id, name_count['error']))
              return self._reply_json({'error': 'Failed to load namespace count: {}'.format(name_count['error'])}, status_code=404)
  
          self._reply_json({'names_count': name_count})
docs: Get the number of names in a namespace
          Reply the number on success
          Reply 404 if the namespace does not exist
          Reply 502 on failure to talk to the blockstack server