code: def skip_incremental(self, *criteria):
          
          if not self.incremental:
              return False
  
          # this is pure convenience, and will probably backfire at some point.
          key = make_key(*criteria)
          if key is None:
              return False
  
          if self.check_tag(key):
              return True
  
          self.set_tag(key, None)
          return False
docs: Perform an incremental check on a set of criteria.
  
          This can be used to execute a part of a crawler only once per an
          interval (which is specified by the ``expire`` setting). If the
          operation has already been performed (and should thus be skipped),
          this will return ``True``. If the operation needs to be executed,
          the returned value will be ``False``.