code: def _prepare_headers(self, request, filter=None, order_by=None, group_by=[], page=None, page_size=None):
          
  
          if filter:
              request.set_header('X-Nuage-Filter', filter)
  
          if order_by:
              request.set_header('X-Nuage-OrderBy', order_by)
  
          if page is not None:
              request.set_header('X-Nuage-Page', str(page))
  
          if page_size:
              request.set_header('X-Nuage-PageSize', str(page_size))
  
          if len(group_by) > 0:
              header = ", ".join(group_by)
              request.set_header('X-Nuage-GroupBy', 'true')
              request.set_header('X-Nuage-Attributes', header)
docs: Prepare headers for the given request
  
              Args:
                  request: the NURESTRequest to send
                  filter: string
                  order_by: string
                  group_by: list of names
                  page: int
                  page_size: int