code: def is_all(self) -> bool:
          
          first = self.sequences[0]
          return isinstance(first, tuple) \
              and first[0] == 1 and isinstance(first[1], MaxValue)
docs: True if the sequence set starts at ``1`` and ends at the maximum
          value.
  
          This may be used to optimize cases of checking for a value in the set,
          avoiding the need to provide ``max_value`` in :meth:`.flatten` or
          :meth:`.iter`.