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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_all(self) -> bool: """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`. """

        first = self.sequences[0]
        return isinstance(first, tuple) \
            and first[0] == 1 and isinstance(first[1], MaxValue)