validSequenceDetermines whether a particular continuation of a sequence is valid. This is used to restrict invalid sequences such as those used in start/continue tag-based chunking or could be used to implement tag dictionary restrictions.
i- The index in the input sequence for which the new outcome is being proposed.
inputSequence- The input sequence.
outcomesSequence- The outcomes so far in this sequence.
outcome- The next proposed outcome for the outcomes sequence.
- true is the sequence would still be valid with the new outcome, false otherwise.