code: def group(*blueprints, url_prefix=""):
          
  
          def chain(nested):
              """itertools.chain() but leaves strings untouched"""
              for i in nested:
                  if isinstance(i, (list, tuple)):
                      yield from chain(i)
                  elif isinstance(i, BlueprintGroup):
                      yield from i.blueprints
                  else:
                      yield i
  
          bps = BlueprintGroup(url_prefix=url_prefix)
          for bp in chain(blueprints):
              if bp.url_prefix is None:
                  bp.url_prefix = ""
              bp.url_prefix = url_prefix + bp.url_prefix
              bps.append(bp)
          return bps
docs: Create a list of blueprints, optionally grouping them under a
          general URL prefix.
  
          :param blueprints: blueprints to be registered as a group
          :param url_prefix: URL route to be prepended to all sub-prefixes