Previously, SequenceSet modification methods would raise a frozen error when it updated its internal data structure (currently implemented as an array of arrays), which was "can't modify frozen Array: [int, int]". This was unexpected, confusing, and misleading.
This changes the SequenceSet modification methods to raise the expected FrozenError prior to attempting to modify the internal data structure.
Previously, SequenceSet modification methods would raise a frozen error when it updated its internal data structure (currently implemented as an array of arrays), which was "can't modify frozen Array: [int, int]". This was unexpected, confusing, and misleading.
This changes the SequenceSet modification methods to raise the expected FrozenError prior to attempting to modify the internal data structure.