code: def GET_blockchain_num_names( self, path_info, blockchain_name ):
          
          if blockchain_name != 'bitcoin':
              # not supported
              self._reply_json({'error': 'Unsupported blockchain'}, status_code=404)
              return
  
          include_expired = False
          
          qs_values = path_info['qs_values']
          if qs_values.get('all', '').lower() in ['1', 'true']:
              include_expired = True
  
          blockstackd_url = get_blockstackd_url()
          num_names = blockstackd_client.get_num_names(include_expired=include_expired, hostport=blockstackd_url)
          if json_is_error(num_names):
              # error
              status_code = num_names.get('http_status', 502)
              return self._reply_json({'error': num_names['error']}, status_code=status_code)
  
          self._reply_json({'names_count': num_names})
          return
docs: Handle GET /blockchains/:blockchainID/name_count
          Takes `all=true` to include expired names
          Reply with the number of names on this blockchain